Aug 11, 2012

Castlevania III RAM and ROM offsets

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Last Update: 2013 / 02 / 18

Just in case my computer dies and I lose the RTF file I've been keeping my notes in, I will post my notes on the address indexing in CV3. That is, where Trevor's and enemy's coordinates are stored in the RAM, where the bounding box offsets (so-to-speak, since there aren't really bounding boxes) are stored, as well as image speeds and other alarms. All that fun stuff will be noted here.

There are up to 22 instances addressed at a time. Trevor always has the lowest address, then enemies, then 5 torches or lanterns, then 5 candles. Item drops use the same address as the enemy, torch or candle they were dropped from. The whip is at X:$13, then the three subweapons. I think X:$17 is reserved for the ally swap, while X:$18 is reserved for the subweapon HUD display.

RAM pages 4 through 7 are used, most of the data being stored in pages 4 and 5. Page 6 is frequently used for alarms or -- in the case of sinusoidal movement -- storing xstart and ystart. Pages 6 and 7 are used for the tile map(s).

Some non-ranged addresses will be included as well. Anything in page 0 is likely unique. An (R) denotes a ranged set of values. A (C) denotes a cascading set of values, meaning they are updated multiple times each step, usually for PPU purposes. All addresses listed as "Sprite index" or "Image index" relate in one way or another to the sprite displayed. Addresses listed below use the lowest index in the ranges (see above).

The US version has many offsets changed due to changes in coding. ROM offsets are often different between versions. RAM offsets in the Zero Page are one byte lower in the US version.


Instance Mapping in the X Register

Up to 28 (0x00 - 0x1B) instances can be mapped out into any room. Certain instance mappings are reserved for specific types. Addresses after 0x17 are used for special cases and as such some indirect addresses exclude them. Below is a list of each mapping.

0x00  Trevor or Ally
In many situations, especially when another instance is already mapped into the X register, this mapping is ignored and variables are referenced directly, such as $0438 instead of $0438,X. If you do see a variable referenced with a 0x00 X register, you're probably within a loop, such as a drawing loop.

0x01-0x0D  Hostiles
Most everything is spawned within free range. Most projectiles spawn within the range of 0x0A to 0x0D, limiting the number of projectiles on screen typically to 4 at a time. Axe Knights are an exception to the rule. 

0x0E-0x12  Luminaries
These higher values are reserved for candles, torches and such. 

0x13  Primary Attack
This is reserved for Trevor's whip or an ally's primary attack.

0x14-0x16  Item Attacks and Spells
Secondary attacks occupy this range.

0x17  Ally Icon
The sprite info for the ally icon is stored here (used in the draw phase).

0x18  Item Sprite
Secondary attack icon info is stored here (used in the draw phase).


PRAM Addressing

$E249 Sound AddressThe value in the accumulator specifies a sound or music to play

$E2D0 PRAM Bank
Set the current bank to the value in the accumulator.

$F543 Step Beginning
Essentially the start of  each step iteration as far as anyone attempting to hack the game would really even care about. Everything before it is technical stuff and drawing code, pretty much.

$FCDE Trevor's Collision Detection
The accumulator holds the relative x-offset to check, while the Y-register checks the relative y-offset to check for collisions with the tile map.



WRAM Addressing

$0011 Attack height (and miscellaneous)
Used for lots of temporary variables, but especially useful when trying to watch death sequences.

$0012 Temporary sprite_index
Used to keep track of $007F and $0565. Adds #$08 to Trevor's y when ducking ($0565==#$1C).

$0015 Temporary y
Used to keep track of $0041C when attacking.

$0018 Room loader
Not sure exactly, but when it's set to 4 the room loads. When it's set to 5, the screen goes black.

$0019 Room loader phase
See above. Handles blacking out the screen when restarting the room, among other things.

$001B Random line ($001A in US version)
This is incremented by 1 every step. It's used for randomization purposes and results in a linear pattern whereby a function X will return the same result X[n] steps later and X[n+1] will always be the same when n is a linear function. Of course, making n a non-linear function will yield results closer to what one would consider "random".

$001D 
Set to 2 when $002C is #$06 (transitioning stairs). One of the many Pause variables.

$001F


$0020 Random bump ($001F in US version)
While $001B is used most for random actions, this will vary things up a bit. This gets incremented and then $001B is added to it. This is done repeatedly between iterations. Basically, in GM terms, thisi is run between the last Draw event and the first Begin Step event.

$0028 Controller press
Used to check if a new button on the controller is pressed.

$002A Controller hold
Each button press adds a specific value to this. Opposites will cancel each other out, though, at least with my I/O setup. Right adds $01, left adds $02, down adds $04, up adds $08, Start adds $10, Select adds $20, B adds $40, and A adds $80. The highest value is $FA (Start, Select, B, A, left and up. 

$002C Cinematics controller
By default it's #$03. Set to #$08 when walking through a door. Set to #$06 when climbing stairs to another room, then to #$07, then to #$01, then to #$04 if it's a vertical room next, then increased so it's #$05 in the next room; if it's a horizontal room it's just increased from #$01 twice so it's #$03 again. In a new stage it's set to #$00 then increased, then set to #$03 or #$05.  
Gets set temporarily to #$19 when whip upgrade is collected and then reset back to #$03. 
Set to #$11 when soul crystal is retrieved or at Clocktower exit -- a value of #$11 at least is for converting time and hearts to score. 
Set to #$18 when walking out of the tower and when at the auto-walk door in the forest. So a value of #$18 is for auto-walking.
Set to #$1E when fleeing Grant's tower or exiting the Clocktower, then to #$17, then to #$1F, then normal stage start settings -- this appears to be normal behavior for a scripted automatic stage transition.
Set to #$09 when climbing stairs to the cloudy areas in Sypha's stage and then set to #$0A so it's actually set at #$0A throughout that room.
Set to #$0B when changing characters.
Set to #$0F for entering a room with auto-climb stairs (Forest, Main Hall). The next stairs out (the auto-climb) set it to #$10.
Set to #$1A when Sypha casts her ice spell in freezable water. After the water freezes over, this gets set to #$1B and is used to prevent conveyor tiles from moving.

$002D Pause
I/O state $00F8 is checked shortly after I/O receipt, so this is a high priority variable.

$002E Stage clear
This gets set when you defeat the boss and the soul shard drops.

$0032 Flash timer
Set when whip upgrade is picked up. Trevor cycles through sprite palettes while this counts down.

$0034 Stage
This is the first value found in reVamp's room editor. Ex., 02:01.02. This gets displayed plus 1.

$0035 Block
This is the middle value found in reVamp's room editor. Ex., 02:01.02. This gets displayed directly. It is increased by 1 when walking through a door.

$0036 Sub-room
This is the third value found in reVamp's room editor. Ex., 02:01.02. This never gets displayed. These are not sequential. Walking down stairs decreases it. A safety check is in place to make sure if it's #$00 before going down stairs that it becomes #$01, yet most of the time the rooms are set so that doesn't happen.

$0037 Lives
Just setting this doesn't change the display until after Trevor dies. Very efficient!

$0038 CHR 0
This is the first set of sprites loaded. This cannot be changed in reVamp. This affects Trevor's sprites. Spirit partners have different offsets, so you can't just change this to make Trevor look like Grant with a whip. In the PPU, this is the top set of tiles loaded on the left.

$0039 CHR 1
This is the second set of sprites loaded. This cannot be changed in reVamp. This affects Trevor's whip. In the PPU, this is the second set of tiles loaded on the left. Each of the CHR selects can be "cleared" by setting them to $7F.

$003A CHR 2
This is the third set of sprites loaded. This can be changed in reVamp. This affects certain enemies and moving platforms. In the PPU, this is the third set of tiles loaded on the left.

$003B CHR 3
This is the fourth set of sprites loaded. This can be changed in reVamp. This affects certain enemies and moving platforms. In the PPU, this is the bottom set of tiles loaded on the left.

$003C CHR 4
This is the first set of tiles loaded. This cannot be changed in reVamp. In the PPU, this is the top set of tiles loaded on the right.

$003D CHR 5
This is the second set of tiles loaded. This can be changed in reVamp. In the PPU, this is the second set of tiles loaded on the right.

$003E CHR 6
This is the third set of tiles loaded. This can be changed in reVamp. In the PPU, this is the third set of tiles loaded on the right.

$003F CHR 7
This is the last set of tiles loaded. This cannot be changed in reVamp. In the PPU, this is the bottom set of tiles loaded on the right.

$0040 - $0043
This range holds the IRQ (interrupt request) control values. It's technical stuff, but basically the IRQ passes are most importantly used to create the ally swap effect.

$0044 Score (R)
Bytes $0044 through $0046 hold the score formatted in decimal.

$0048 Spirit partner
Sypha is $01, Grant is $02, Alucard is $03, Trevor solo is $FF. 

$0049 Spirit swapped
This is set when Trevor swaps places with his partner.

$004A Trevor's health
Max value is $40. One bar is equal to 4 HP.

$004B Boss' health
During boss fights, this is the same as $067C.

$0053 View origin (Word)
This is the view's coordinates in the room, stored in little endian format. Therefore $0054 can be thought of as the screen value. This affects doors and maybe other things. In horizontal stages, this is the xview, but in vertical stages it's yview.

$0055 View origin fraction
Used for when Trevor's hspeed isn't 1 or 2 exactly.

$0056
Not sure what the use is. This is essentially every 32 pixels in the view, but set outside the view. So when xview is #$00, this is #$FE. Only gets checked when walking left.

$0057 
Same as above, but this one is for the right. 

$005E (W)
Unknown.

$0062 Movement
This is set according to Trevor's movement. If he walks left, this gets set to 0; if he walks right, it's set to 1. It will constantly toggle back to 2, possibly at the start of each step.

$0065 Room orientation
Setting this to anything less than $80 means the room is oriented horizontally. Setting this to $80 or greater means the room is oriented vertically. The chapel in stage 1 is set to $80. (More details in ROM addresses below.) Since there are no doors in vertical stages, this also affects how close to the edge of the screen Trevor can walk to.

$0066 Stairs index (Word)
The PRG-ROM address for the index of values for any stairs in the current room is stored here. 

$0068 Transition state
In door-to-door room transitions, this is the substate. 0 sets up the transition, 1 is a slight delay before the transition progresses, 2 is the first scroll, 3 is a slight pause, 4 is the opening of the door, 5 is Trevor walking, 6 is the closing of the door, 7 is another pause, and 8 is the final scroll.

$0068 Trevor's phase counter
Appears to be a phase counter used during partner changes. Cleared when walking through a door.

$0069 Event object
I think this keeps track of which instance is currently being handled. Since X will change when a projectile is thrown, for example, the program needs to keep track of which value of X points to the instance that created said projectile. When the room starts, this is used to keep track of how many interactive terrains are in the room and is stored for each of those terrain objects.

$006A
Unknown.

$006B Object shift speed
This is dependent upon the room orientation. If the room is oriented horizontally, this value is subtracted from the x-coordinates of all instances except Trevor. If the room is oriented vertically, this value is added to the y-coordinates of all instances except Trevor. If Trevor's in the middle of the view, of a room with multiple screens, this value is added to his x-coordinate in a horizontal stage.

$006C View offset
The game has to tell the NES how far to shift the tiles over. This is how it does it. When Trevor moves, it increases or decreases and the value is passed to register $2005.

$006E Vertical bottom screen
In vertical stages, this is the lowest screen (yview & #$F00).

$0070 Previous orientation
The previous room's orientation is stored here. This is used in room transitions. Roundabout method. If it's negative, the previous room was vertical, which apparently affects what the next room is. Negative $0065 overrides this always.

$0072
Unknown.

$0073 Spawner block
This has a particular function and shouldn't be messed with. It's first set to the current screen ($0054). If xview ($0053)+2 exceeds #$FF, the carry bit is set and added to $0073. The value of xview+2 is then shifted left and then $0073 gets rotated  left, so if xview+2<<1 is greater than #$FF, $0073 becomes $0073<<1|1. This is repeated one more time. The resultant determines what the lowest spawner block (those 64px wide divisions that can only hold one spawner) offset will be. The value is then shifted left and used as an index pointer for the spawner offset.

$0075 Boss lock
This will freeze screen movement when a boss is present.

$0078
This is the max 32px interval of the view used to check against $0057. In other words, I don't know.

$007A Animated backgrounds
Set for stages with animated backgrounds. The value denotes parallax scrolling or which tiles to change. Seems to hold two values (suggested by &#$F0 operation).
NOTE: STAGES WITH PARALLAX BACKGROUNDS (i.e., clouds) CANNOT HAVE ANY INTERACTIVE TERRAIN OBJECTS IN THEM BECAUSE PARALLAX CLOUDS OCCUPY THE SAME RAM OFFSETS AS TERRAIN OBJECTS. 

Known values:
  $10  Stormy Clouds (3-02)
  $11  Wide Clouds (Forest)
  $12  High Clouds (Castle Keep)
  $13  Low Clouds (Castle Keep
  $30  River + Waterfalls (Causeway)
  $40  Clockwork (Dracula's Tower)
  $41  Fast Clockwork (Clocktower)
  $50  Watery Death (Sunken City)
  $51  Watery Death (Sunken City)
  $52  Watery Death (Sunken City) 
  $60  Watery Death (Sunken City)
  $71  Rising Water (Sunken City)
  $80  Collapsing Bridge (Causeway)   
For the Watery Deaths, the lower bits set the depth at which the splash occurs. For #$5X range, these values are adjustable at PROM address 0x38C5D to  0x38C60. For the #$6X range, these are hard-coded, with #$60 being at depth #$C0 as defined in PROM address 0x38C2F, whereas any other value is the default screen depth of #$E0 (in other words, #$61 to #$6F are junk ranges and I have no idea why they are there other than as remnants of previous code).

$007B Timer (Word) 
Converted into decimal and stored here. What you see is what you get. 

$007D Wounded timer
Set when Trevor takes damage and becomes invincible. It counts down each step if set. While set, every other step toggles Trevor's visibility state.

$007E Damage received
When an enemy hits Trevor, the damage level is temporarily stored here.

$007F Special values
See ROM Addresses section of same title. Handles special attributes of certain rooms.

$007F Height offset
From what I can tell, this is initially set to the object_index, since each character has different heights. When ducking, this is set to object_index+4, which in most cases is the same.

$0081 Hearts
The game converts the heart count to decimal format before storing to this address. The highest this can be is 99 (hard-coded).
                                                                                                                                                        
$0082 Subweapon (R)
Axe is $01, Cross is $02, Dagger is $03, Holy Water is $04, Sypha's fire is $05, Sypha's ice is $06, Sypha's water is $07, Grant's dagger is $08, Grant's axe is $09, Alucard's fireball is $0A, Stopwatch is $0B.

$0084 Subweapon multiplier


$0088 Effects
When  terrain (conveyor or mud) hinders Trevor's movement, this gets set
  $01  Riding platforms or frozen enemies
  $02  Can only walk right
  $03  Uknown/No effect
  $04  Unknown/No effect
  $05  Teeter-Totter
  $06  Gears
  $07  Mud
  $08  Waterfall
  $09  Convey right under waterfall
  $0A  Convey left
  $0B  Convey right
  $0D  Petrified 
  $0E  Auto-Walk

$008A
Yet another phase counter for Trevor.

$008B Whip level


$008D Knockback direction
Set to determine direction Trevor gets knocked back when wounded.

$008E Force speed
When Trevor's movement get affected by some object (enemy or terrain), this gets set to the spawn ID and used to knock back or lift Trevor.

$0090
Ride type. This gets set when Trevor is on moving terrain.

$0091
Ride ID. For gears, this is the value of the tooth closest to Trevor.

$0092
Denotes if on a small gear (0) or big gear (1) when riding gears.

$009C
Temporary holder for $002C when collecting whip upgrade.

$009D
Temporary holder for $009E when collecting whip upgrade.

$009E
Temporary holder for $0062 when collecting whip upgrade. Yeah, it gets confusing.

$00A2
Set if the right tile is checked in a tile map read.

$00A3 thru $00A6
Temporary holder for $0040 thru $0043 when changing characters.

$00A7
Temporary holder for $2C when changing characters.

$00A8 Stopwatch status
Set to 1 when the Stopwatch is used. This affects if $00A9 is decremented.

$00A9 Stopwatch timer
This is set to

$00AA
Unknown

$00AC Frozen fall counter
When falling off a frozen enemy or when an enemy Sypha is standing on thaws out, this timer gets set and decremented. It serves no visible purpose, so maybe was a carry-over from a plan to allow the player brief invulnerability from thawed enemies.

$00AD
Unknown 

$00AF
Unknown

$00B0
Related to the Stopwatch, it seems. 

$00B4
Gets set momentarily when colliding with a whip powerup.
On the Name Entry and Password screens, this is a counter for the fade-in and fade-out transition codes. The corresponding values added to each palette entry are: #$00, #$F0, #$E0, #$D0, #$C0, and #$FF. The #$FF marks the break. All this does is shift the palette entries up one row to darken the colors. If a value becomes negative, the entry is set to $0F (black).

$00B5
On the Name Entry and Password screens, this is the timer between steps in the fade-in and fade-out transition codes.

$00B6 Rough landing
If Trevor falls from too high up, this gets set when he lands, preventing movement until it ticks down. 

$00B7 Boss fight
This gets set depending on which boss is fought.

$00BC Death pause
When Trevor dies, this gets set to #$80 to prevent damage calculations and pause the game while Trevor goes through his death animation and the room restarts.

$00BD
Unknown

$00BE
Unknown

$00BF
Unknown

$00C1

$00C2

$00C5 Horizontal lock
When this is set, the view will not move left, preventing Trevor from going less than 16 pixels from the left edge. This is set when a crumbling bridge is encountered, for example. This is not set by bosses.

$00C9

$00CA

$00CB Enemy drop counter
Incremented and checked when random check passes on enemy death ($001B &amp; $07). When less than $05, enemies that pass the check drop a small heart. Every fifth enemy that passes the check has a 50% chance of dropping an Axe, 25% chance of dropping a Dagger, and 25% chance of dropping a Stopwatch. If Trevor already has the subweapon, a small heart is dropped instead. Potential drops are stored in PRG-ROM $04:BE93 thru $04:BE96 (see Item drop below).

$00CC
Holds previous value of $0088.

$00CD Vertical room ceiling
For vertical stages, this is the height at which Trevor will bump his head. Tile collisions will always return #$00 in that case.

$00F0 (R)
Unknown

$00F4 Breakable wall status (R)
This gets set to FF for each breakable wall in a block that gets destroyed. The variable that determines if a wall can be destroyed is set based on this. Along with the other variables between $00F0 and $00F7, this gets reset when changing rooms obviously.

$00F8 I/O press
Checked if #$00 or #$10 when $002D is cleared.

$00FA Previous I/O
Same as $002A. This is essentially the previous button.

$02FC Tile dump (R) (C)
The TSA map is dumped here. The tile map is generated on the fly. The TSA map for the current stage is loaded into the PRG-ROM bank and evaluated on a tile-by-tile basis. The tile values correspond to their relative offset in the PPU. Tiles of value #$C0 or higher fall under the "universal interactive" category (in other words, spikes). This range of tiles is actually reserved for common sprites, but stationary spikes are included in this subset. Below is a list of value ranges used to determine the tile map.
    $DC - $DD Ceiling Spike
    $DE - $DF Floor Spike
    $E4 - $E5 Trap Door (counts as empty)

$0347 Palette (R) (C)
The background palette is stored here.

$0400 Image single (R)
Just making up names here. This is the actual frame displayed, whereas the image index is the offset for the address this points to. So sprite displayed is offset by image_single+image_index.

$0413 Whip damage

$0418


$041A (Word)
Unknown. Gets cleared when $002C==#$08 or #$1B.

$041C Y-coordinate (R)


$042F Attacking y
This gets increased by 8 when ducking (but not jumping, since Trevor stands when jump-attacking).

$0434 Y-coordinate of subweapon icon


$0436 Y-coordinate of Breakable Blocks (W)


$0438 X-coordinate (R)


$0438 X-coordinate of Breakable Blocks (W)


$0450 X-coordinate of subweapon icon


$0454 Sprite palette (R)

$046C

$0470 State (R)
Care when editing these. For Trevor, $00 is visible and $80 is invisible. Collecting a whip powerup will force this to #$00 so Trevor is visible during the shimmer effect. For luminaries, this seems to just be the type. For enemies, this determines if the enemy will move or stand still, be visible, or even interact with Trevor at all. Each bit serves a specific function:
 $HGFEDCBA
  A  Destroyed 
  B  Frozen
  C  Unknown
  D  Forces byte H
  E  Illusion
  F  Unanimated
  G  Moving
  H  Invisible
Clearing the lower nybble seems to have no effect for enemies. The lowest bit of the lower nybble should never be set (i.e., no odd numbered values), as this will instantly destroy the enemy. The lowest bit of the upper nybble will render the enemy illusionary -- Trevor will not be able to attack it, nor will it be able to attack Trevor. For some reason, enemies like Sword Skeletons set bit F when attacking, probably some unknown mechanic that made it necessary. Not sure what bit C is for. It's set for most enemies. It's cleared for Medusa Heads.

$048B
Unknown

$048C PPU address (R)
This determines which row in the PPU to read. Probably shouldn't mess with this.

$04A5

$04A8 X-scale (R)
Sprites face left in the ROM, so a value of 0 flips the sprite so it faces right. This is unnoticeable with torches and lanterns, but does have a slight effect on candles.

$04C0

$04C4 Fractional X-coordinate (R)
When integral speed is added to the X-coordinate, the X-coordinate increases, but not when a fractional speed is added (e.g., X=0; X+1/4=0). So what happens to that fractional speed? It gets added to this instead, which rolls over to the X-coordinate when the carry bit is set..

$04DB Fractional Y-coordinate (R)


$04F2 Integral horizontal speed (R)


$0505
Part of a partner swap counter, it seems. Adds #$10 to the hit alarm when it reaches 8.

$0509 Fractional horizontal speed (R)
Any speed value less than 1 is stored here as an 8-bit floating point (e.g., a speed of 1/4 will set this to #40, since #100 / 4=#40).

$051C
Denominator of partner swap counter (see $0505).

$0520 Integral vertical speed (R)
Very important. Not only does it move the instance, it is checked when climbing stairs.

$0537 Fractional vertical speed (R)


$054E Object index / PRG-ROM offset (R)
Variables specific to each instance are found in the PRG-ROM. This byte tells the game which address to look up. This is the same as $0048 for spirit partners. Always keep luminary values between #$80 and #$82; all inappropriate values pose a risk of actually crashing the game.

$0561 Whip level
This is the number of whip upgrades collected.

$0565 Action state(R)
Don't mess with it, as it more than likely freeze up on you. Very important variable, at least for Trevor. It can have the following values:
    $02 Stand Idle
    $04 Walking
    $06 Jump Start
    $08 Jumping
    $0A Ducking
    $0C Falling
    $0E Walk To Stair
    $10 Start Climb
    $12 Stair Idle
    $14 Stair Climb
    $16 Stair Transition
    $18 Stand Attack
    $1A Jump Attack
    $1C Duck Attack
    $1E Stair Attack
    $20 Stand Item (Stand Attack for Alucard)
    $22 Jump Item (Jump Attack for Alucard)
    $24 Stair Item
    $26 Knocked Back
    $2C
    $2E Dead
    $30 Alucard Henshin! / Grant Wall
    $32 Alucard POOMF! / Grant Ceiling
    $34 Alucard Bat / Grant Reach Ceiling-to-Wall
    $36 Grant Hug Ceiling-to-Wall
    $38 Grant Reach Wall-to-Ceiling
    $3A Alucard Ascent / Grant Hug Wall-to-Ceiling
    $3C Alucard Revert / Grant Reach Wall-to-Floor
    $3E Alucard POP! / Grant Hug Wall-to-Floor
    $80
     .  Any above value ORed with #$80
     .  will freeze Trevor in that action
     .
    $BE 
Values $06 and $10 are logical. When he jumps, Trevor doesn't apply horizontal movement on the first frame, so it's not until $08 that he starts moving. When transitioning from the ground to stairs, certain variables are set, so this transitional phase is handled by $10. Value $0C is only applied when falling off a ledge. For jumps, it's always $08 (or $1A for jump attacks or $22 for jump items). 
For bosses, this determines their next action, usually.

$0578 (R) Weapon phase
 Same role as $0565 for Trevor, this tells the weapon what to do. For Trevor's whip and Sypha's staff, it just tells them to update their coordinates.

$057C Image speed (R)
Counts down to 0 then changes image index upon rolling over.

$0593 Image index (R)
This one is most definitely close to image_index. When Trevor walks, it cycles {0,2,4,6}. 

$05AA Sprite offset? (R)
No clue what this is for, but it is set at the same time the PPU address is set for instances, so clearly it's related to sprites. Since it's usually greater than 8, I think it's a sprite definition offset.

$05C1 Fall switch
Although this is a range, this specific use applies only to Trevor. When he falls, this is set to 1. This is so the game knows whether to increase the jump offset or decrease it (see below).
(For enemies and lanterns, this seems to be a phase counter. Don't mess with it.)

$05D4
Holds Trevor's action state temporarily when hit or his x when changing partners.

$05D8 Jump offset / Fall height
Although this is a range, specific use applies only to Trevor. This is set to 9 when he jumps and increased each step, then stored in the Y register. This is used to retrieve the integral vertical speed. When the value retrieved for speed is $81, it decreases and the integral speed is inverted. When the value retrieved is $80, the speed is set to $06 and this address no longer changes. Upon landing, if this is $00 (in other words, integral speed is $06), Trevor lands roughly.

$05D9 Item drop (R)
This is where candle drops are stored. Any value below $83 seems to crash the game, while values over $A0 cause graphical glitches. Here are the known useable values:
    $83 Axe
    $84 Cross
    $85 Dagger
    $86 Holy Water
    $87 Stopwatch
    $88 Sypha's fire
    $89 Sypha's ice
    $8A Sypha's water
    $8B Grant's Dagger
    $8C Grant's Axe
    $8D Alucard upgrade 1 (upgrades whip to 1)
    $8E Alucard upgrade 2 (upgrades whip to 2)
    $8F Nothing? (looks like whip upgrade but no effect)
    $90 Mystery Meat
    $91 Invincibility Potion (duration = $B4)
    $92 Rosary
    $93 100 Point Bag
    $94 200 Point Bag
    $95 400 Point Bag
    $96 700 Point Bag
    $97 1 k Point Bag
    $98 2 k Point Bag
    $99 4 k Point Bag
    $9A 7 k Point Bag
    $9B 10G Point Bag
    $9C 1UP
    $9D Big Heart
    $9E Small Heart
    $9F 2x Multiplier
    $A0 3x Multiplier
    $A1 Fake Candle (can be useful glitch)

$05D9 Boss timer (R)
This is set when a boss appears and then counts down before starting the boss battle. 

$05EB Hit alarm
Set to #$20 when Trevor is hit. Reverts to previous action when zeroed. Used as numerator in partner swap counter (see $0505).

$05EF Various / Timeline index
Somehow affects room transitions for Trevor. On stairs, this is the direction he's facing, basically. For enemies, this is essentially the map for the action scripts. For enemies, this is essentially a timeline index in Game Maker terms, a reference point for a set of commands to be executed each step. When not #$00 or #$80, the code will branch and perform a specific action. Thus $05C1,X can be thought of as a timeline position. For bosses, typically most activity occurs outside the timeline; this makes reading boss code confusing.

$0602
Cleared when Trevor is hit. Rarely set, so not sure what this is actually for. Decreases hit alarm for Alucard if set. Used as integral for partner swap counter (see $0505).

$0606 Alarm / Starting Y (R)
Some enemies use this as an alarm, others use it to store the starting x or y coordinate for use in sinusoidal movement.

$0619 Ally Swap Y-Offset
This is used for the IRQ pass in conjunction with $0630. Don't sweat it.

$061D Stair step
This is the alarm that determines how long Trevor climbs stairs until the next input check.

$061E Enemy timer (R)
This one is almost always a dedicated timer for enemies.

$0630 Whip damage
How much damage the whip deals, shifted 4 bits.

$0630 Ally Swap IRQ Toggle
When swapping allies, this toggles and is subtracted from $0619 to create the ally swap effect.

$0633 Counter (R)
For enemies like crows, this counts how many dives they attempt. 

$0645 Spawn ID (R)
For candles, this is the object index. For enemies, this is the spawner ID that spawned it.
For Death, this is his appearance timer (instead of using $7F3).

$0657 Damage (R)
Not sure what this holds for Trevor. For enemies and projectiles, this is the damage. This determines the level of damage, (light, normal, heavy). Hard Mode and any stage from the Abandoned Mines upward will typically increase damage. 

$0669 Damage received (R)
This is how much damage an enemy has taken from Trevor.

$067C Health (R)
This is duplicated for bosses. All enemies have health, even "indestructible" ones. A blood skeleton can be slain if enough damage is dealt to it, but time will probably run out before it dies.

$068D Hit (R)
This gets set when hit by the whip.

$06DC Stopwatch state
This is the same as $00A8. Not sure why this extra byte is used. This is the value actually checked by instances each step, not $00A8. So if you want a permanent Stopwatch, this is the byte to set.

$06E0 Tile map (Word) (R)
The tile collision map is read by columns, starting with the leftmost column on the screen. Only the top-left tile of each metatile is read. It is refreshed so only the tiles in the vicinity are registered. The map is very simplistic. One Word is equal to one TSA. Each Word reads left-to-right, top-to-bottom in the TSA. The address is retrieved for y+16 (less 32 to account for the status bar). Words can be visualized like so:
  $ABCD 
corresponds to 
    AB
    CD
An example demonstrating this can be seen here.
The following values exist:
    $0 Empty
    $1 Mud
    $2 Conveyor right
    $3 Conveyor left
    $4 Crumbling ledge
    $5 Ceiling Spike
    $6 Solid
    $7 Floor Spike
    $C Crumbling (increments to $F)
Each of these are treated as solids when approached from the side. Because of this, you cannot have mud on top of a conveyor and expect the conveyor to pull you through it, but it will pull you out if you sink to the conveyor at just the right spot. ("Pull out, Peggy! You hit an artery!") The conveyor flags apply to the blocks under the water, not the water itself (which is $0). Because of this, you cannot have water and crumbling ledges at the same time (as nifty as that would be). That's not to say you couldn't program such a gimmick, but it's just not already incorporated. You can put mud over a collapsing ledge, if you wanted to for whatever reason. Trevor would have to jump out of the mud to avoid from falling. Crumbling ledges do not automatically disappear and falling ledges do not automatically fall. These addresses only affect the collision states. The spikes are essentially the same. I don't know why they have two separate values, as touching either of them from any direction will kill you. Any of the other solids can be placed over these, although only mud or crumbling blocks would make sense over a spike.

$0770 Solids definition (R)If a room has special tiles (such as conveyors or mud), their offsets are stored here. Byte $0776 and $0777 are always #$80. Bytes $077E and $077F are always #$C0. Bytes $0770 thru $0775 define the lower region of tiles whose PPU offset is less than $80, while $0778 thru $077D define the lower region of the specific tiles whose PPU offset is less than $C0. Six instances of a PPU offset translate to a tile map value of #$6. In other words, if you wanted three of the tiles to be mud, you'd specify the range of tiles to be treated as mud in byte $0778. If you wanted no tiles from a specific half of the PPU, you'd set all corresponding bytes to that max offset.

$0780 Background Animation Frame
Bone Dragon King uses this; don't remember seeing it used outside of him. There are 3 frames of animation for CHR 5 in the clocktower and sunken city.

$0781 Background Animation Speed
Bone Dragon King uses this; don't remember seeing it used outside of him. This is how frequently the CHR 5 (half the background tiles) change during his fight.
 
$0782 Epilogue partner
Needs to be set before picking up Dracula's crystal, I think. This is the value read for determining offsets used in the epilogue. This is the same as $0048.

$0785 Epilogue text offset
This increases with each pass of the epilogue timer. It is used to retrieve the index for the next line of text or the end of the epilogue.

$078A Epilogue timer
This is how fast the next line of text is loaded into the PPU during the epilogue. Messing with the scroll speed means you may need to edit this as well (see ROM Addresses). 

$0790 Interactive terrain index (R)
Seems to hold $0069 for gears and crushers. Maybe other objects as well. 

$0790 Path at fork (R)
When the road forks, four variables are set. They determine the sprites to use for the path marker on the mini-map. 

$0790 Password Icon Value (R)
On the password entry screen, each cell has a value of 3n and each icon has a value of 1, 2 or 3. The icon value is added to the cell value, which is essentially the password.

$079D Byte 8 (R)
I don't know what else to call this. It holds byte 8 of breakable blocks (see ROM Addresses). Since this is written when X is #$1A or #$1B (and X cuts off at #$1C), only two values are found here and $7B8.

$07A1 Terrain screen
Seems to be a tracker for the current screen value relative to the first interactive terrain object.

$07A2 Active terrain
This is the number of interactive terrain objects (gears, crushers, breakable blocks, dripping water, etc.) in the view (horizontal stage) or the accessible room (vertical stages).

$07A7  Breakable Block Status (W)
Set to #$80 when the block is destroyed.

 $07B1 Dual-layer wall (R)
For breakable walls, this is set when the wall occupies two tiles. 

$07B3 Broken bottom tile (R)
For breakable walls, this is set to $FF when the lower wall is broken.

$07B5 Broken top wall (R)
For breakable walls, this is set to $FF when the top wall is broken.

$07B7 Wall ID (R)
This is the ID of the wall in the room, used to offset from $00F4. 

$07C2 Spawner offset (R)
This stores the ID of the enemy spawners. This is the same value as seen in reVamp. The value is shifted left 1 bit to retrieve the address indexed at $028533.

$07C8 Spawner count (R)
This gets incremented each time an enemy is spawned. This gets retrieved, shifted left, then used to offset the values retrieved by $7C2,X. For enemies that can only spawn once, this gets set to 1 when the enemy can be spawned and then cleared when once the enemy is spawned.

$07CE Spawn timer (R)
So far only used by non-flickering Ghost to delay spawning.

$07D4 Spawn y-coordinate (R)
This is the y-coordinate in the target screen for the spawner. This is where the enemy will be generated whenever the spawner code is called. Note that Spiders are hardcoded to start from #$30.

$07DA Spawn x-coordinate (R)
This is the x-coordinate in the target screen for the spawner. This is where the enemy will be generated whenever the spawner's code is called.

$07E0 Off-screen status (R)
This is cleared as long as the spawner is on the screen. As soon as the spawner leaves the screen (via x+screen_shift) this gets set, preventing its code from running. 

$07E6 Spawned X register (R) / Instance value 1 (R)
This stores the X register value used when an enemy was successfully spawned. When a spawner is first loaded, the first of any special instance-specific value is loaded here.

$07EC Various
This increments slowly for Bone Dragons. It's used to handle movement.
For the Giant Bat, this stores the instance ID of the main bat.
For Big D, this is his form (0=sorceror, 1=floating heads, 2=Pazuzu).


$07ED Various
This controls how many blocks comprise a collapsing bridge. 
When a Bone Dragon is present, this controls the xscale of the ribs and fireball.
For the Giant Bat, this is the current state of all bats (not sure why it uses an extra byte).

$07EE Bone Dragon alarm
For Bone Dragons this counts down from $30. When it reaches 0, the Bone Dragon opens its mouth and this is set to $10. After the Bone Dragon spits, it's set to $80 and the Bone Dragon closes its mouth.
For Death, this is the number of scythes he can throw.

$07EF Bone Dragon spit
When the Bone Dragon finally attacks, this is set to #$01 briefly and the fireball is generated on the next pass.

$07F3 Boss State
Bit confusing to call it this. It's set to #$80 when the boss first spawns and while set to this it waits until Trevor is in range of the boss, at which point it is set to #$00 when the boss is active. When the boss dies and goes through its death sequence, it's set to #$01. When the boss is finally destroyed and the soul shard is supposed to drop, this gets set to #$02. When the soul shard finally appears, it's set to #$03.

$07F6 Hard mode
This is set when you play in hard mode. It's also used in password generation.

$07F8 Name (R)
Bytes $07F8 thru $07FF store each letter of the name, with A=$50, B=$51, and so on.



Some ROM addresses!


Scene Tiling
For stages, tile square assemblies are used (see below), but for simple aesthetics, tiles are placed individually row by row. There are shortcuts, however. When a tile is put in the room repeated 4 or more times, two values are used. The first value specifies how many tiles to draw, while the second value specifies which tile to draw. Afterwards, either another repeating tile is written or the next address in the PPU is set to a value greater than $80. The difference between that value and $80 is how many tiles will be specified individually, beyond which point the next value is a repeated tile. So for example:
    05 DE 81 B1 10 00 04 DE 82 8A 8B
In the above example, first tile $DE will be drawn in the room 5 times. After the fifth one is drawn, tile $B1 will be drawn next. After that, tile $00 will be drawn 16 times. Then tile $DE will be drawn 4 more times. Finally, tiles 8A and 8B will be drawn. Below are some scene addresses tiled as such. Below each scene's tile map is the CHR data as well. Loading $7F into a CHR select will result in a blank tile set.
    $033651 Intro Castle
      $00646F CHR 4
      $006473 CHR 5
      $006477 CHR 6
      $00647B CHR 7
        CHR 0 thru CHR 3 are set to #$00 and #$01.
    $00B552 Title Screen
      $006BC7 CHR 3 (path markers make up the lightning here)
      $00647F CHR 4
      $006480 CHR 5
      $006481 CHR 6
      $006482 CHR 7
    $00B552 Main Menu (yes, it's the same as Title Screen)
      $03E3BE CHR 0
      $03E3C2 CHR 1 (CHR_0+1, can't be changed easily)
      $03E3C6 CHR 4
      $03E3CA CHR 5
      $03E3CE CHR 6
      $03E3D2 CHR 7
    $007BE3 Name Entry
      $007414 CHR 0
      $007415 CHR 1
      $007416 CHR 2
      $007417 CHR 3
      $007418 CHR 4
      $007419 CHR 5
      $00741A CHR 6
      $00741B CHR 7
    $033302 Password
        Same CHR set as Name Entry
    $00668D Prayer
      $006547 CHR 0
      $00654B CHR 1
      $00654F CHR 2
      $006553 CHR 3
      $006557 CHR 4
      $00655B CHR 5
      $00655F CHR 6
      $006563 CHR 7
    $02BDFB Epilogue
      $02B02B CHR 0
      $02B02F CHR 1
      $02B033 CHR 2
      $02B037 CHR 3
      $02B03B CHR 4
      $02B03F CHR 5
      $02B043 CHR 6
      $02B047 CHR 7

Text
The prologue handles a little differently than the title screen. The border around the title screen is drawn. Each line of text is preceded by $80 for a line break and then the x-position of the first tile in that line, with $00 meaning no text. So $80080F would mean a new line is started and tile $0F would be drawn at x:#$08 of that line. At the end of the code, $8100 denotes a page break. Below each text address is the CHR 4 thru CHR 7 range loaded at the time. Diacritics (in Akumajou Densetsu) are drawn on the previous line, but written immediately after the character they follow.
    $03DC1D Prologue Paragraph 1
      $006483 thru $006486
    $03DD12 Prologue Paragraph 2
      $006487 thru $00648A
    $03DDEC Prologue Paragraph 3
      $00648B thru $00648E (Whip)
    $03DEA0 Prologue Paragraph 4
      $00648F thru $006492 (Bust of Trevor)
    $03DF65 Prologue Paragraph 5 (lots of line breaks here)
      $006493 thru $006496 (Trevor overlooking Castlevania)
      $006497 thru $00649A (font)
   The final 12 bytes of CHR addressing are the same as $006493 thru $006496.
The epilogue text is handled quite differently. This time diacritics are handled on separate lines. Each line is assigned an absolute PPU address (written in reverse byte order). When the end of a line is reached, the value $FE is written. When a pause between lines is needed, $FF is written (I think). The same CHR values are used throughout the epilogue.
      $02B203 CHR 0
      $02B207 CHR 1
      $02B20B CHR 2
      $02B20F CHR 3
      $02B213 CHR 4
      $02B217 CHR 5
      $02B21B CHR 6
      $02B21F CHR 7
    $02B95E Epilogue Part 1 (generic)
    $02BC2D Epilogue Part 3 (Grant)

TSA Definitions
TSAs are stored in the ROM left to right, top to bottom, row by row. Solid black is routinely PPU address $00 while solid "sky" is $3D. Each TSA section is preceded by the tile maps for each stage (see below).
  $0182D0 - $187CF Catacombs
  $018EDB - $19EDA Abandoned Mines
  $01A2FB - $1A8FA Main Hall
  $01AC9A - $1B269 Inner Hall
  $01B592 - $1BD51 Castle Keep
  $01C459 - $1C9B8 Causeway
  $01CD94 - $1D143 Swamp
  $01D78E - $1DD8D Alucard's Cave
  $01E3BE - $1E9BD Sunken City
  $01EDFA - $1F3C9 Lookout Tower
  ??????
  $020451 - $20D60 Wallachia
  $02141A - $21965 Clocktower
  $022120 - $2263F Forest
  $022C7D - $232BC Ghost Ship
  $023737 - $23BB6 Tower

TSA Maps
Each tile map is preceded by a byte specifying the size of the room. So $200BA is set to #$02 since the first room takes up 2 extra screens, $2014B is set to #$00 since the next area doesn't take up any extra screens. One vertical screen is 64 bytes. One horizontal screen is 48 bytes. Tile maps read left to right, top to bottom, row by row. Stage 1 is expanded here as an example. For all other addresses, refer to reVamp's room editor (it shows the ROM address for each TSA in the room. Rooms, like stages, are not mapped out in order.
  $020039 Stage 1-02:1 size
  $02003A - $200B9 Stage 1-02:1
  $0200BA Stage 1-01:0 size
  $0200BB - $2014A Stage 1-01:0
  $02014B Stage 1-02:0 size
  $02014C - $2017B Stage 1-02:0
  $02017C Stage 1-02:2 size
  $02017D - $201DC Stage 1-02:2
  $0201DD Stage 1-02:3 size
  $0201DE - $2026D Stage 1-02:3
  $02026E Stage 1-03:0 size
  $02026F - $202FE Stage 1-03:0
  $0202FF Stage 1-03:1 size
  $020300 - $2038F Stage 1-03:1
  $020390 Stage 1-04:0
  $020391 - $20450 Stage 1-04:0
  $01802B Catacombs
  $01886D Abandoned Mines
  $019FF6 Main Hall

Stage CHRs
The CHR for each stage is pretty easy to find in the ROM, as they're in order according to stage, block, and room. CHR 0 is always set to #$00 and CHR 1 is simply CHR_0+1, although these values can be easily modified. CHR 4 is always set to #$40 and CHR 7 is always set to #$43, but these can be modified too.
  $00001F CHR 0
  $00001B CHR 1 offset from CHR 0
  $000F4F CHR 4
  $000F53 CHR 7
  $000275 CHR 2 | CHR 3
  $00018C CHR 5 | CHR 6
The values of CHR 5 and CHR 6 are indexed as Words, with the upper byte used for CHR 6. The range from $00018C to $000274 should include CHR 5/CHR 6 pairs for all levels in order, but this hasn't been tested. Likewise with CHR 2/CHR 3.

Solids Definitions
Solid tiles are pretty easy to define, but care is needed since the number of bytes required to define the solids for each room is dependent on the variety of solids present in that room.
  $0003D2 PRG-ROM Index
  $00042C Definitions
All the definitions are within the $84XX block of the PRG-ROM (by default). All the definitions are follow a simple format of one WORD per solid. The lower byte specifies how many times the solid type, determined by the upper byte, should occur in the Solids Definition in the RAM. It then moves onto the next WORD. The sum of the lower bits cannot exceed 8. The game will increment the X register by 1 every time a value is written to the RAM, which it then ANDs with #$07, branching to the second set of solids definitions and repeating the process. Special consideration is given to Pazuzu's lower tile group ($33), a Konami logo ($36) and a font ($37). The latter two apparently go together, but I don't know when they're actually used -- possibly the ending credits. The standard font is $41 and Konami logo is $72. The Solids Definitions index works the same way as most every other index in the game. The CHR selects are set at the same time.
  $805F + $0034<<1
    ↑ + $0035<<2
          ↑ + $0036<<1 CHR 5 and CHR 6
    ↑ + $0035<<2 + 2
          ↑ + $0036<<1 CHR 2 and CHR 3
    ↑ + CHR 5 - #$44 <<1 Address for CHR 5 solids
    ↑ + CHR 6 - #$44 <<1 Address for CHR 6 solids

Palette sets
Most palette entries only hold 3 values and the game loads these three into the placeholders. Editing the background palette placeholder in reVamp automatically affects all other background colors, but by editing the ROM data directly, it's possible to set 4 different background colors. The palette sets for background colors contain 3 palettes per group. Intro, prologue, name, and password screens have their own separate palettes.
  For the preset sprite palettes, sets 1 and 2 are listed first (Trevor and relics), then #$0F0F0F0F as a placeholder for the room-specific sets, then set 4 (candles and hearts). Only the three colors unique to sprite palette entry 3 for each room is stored.
  Trevor's first color is the default background color apparently. After tweaking with background palettes in reVamp and searching for changes in the ROM, Trevor's palette was the only thing that changed. That really sucks. 
  $4BE Palette script
  This is the start of the palette loading code. 
  $00066F Palette set used (R)
  This is actually stored in order, addressed incrementally when rooms changed. The order of palette sets used will be sequential regardless of room index. Clocktower decrements when climbing back down, even though reVamp treats them as separate rooms.
  $6DE Status bar
  This is quadruplicated as a placeholder. Of course the first value is the status bar's palette always.
  $0006EF - $0006F5 Set #$00
        thru
  $000869 - $000871 Set #$2A
  $0008EF Trevor
  $0008F3 Relics & skeletons
  $0008F7 Room palette placeholder
  $0008FB Hearts and candles
  $000900 Grant
  $000926 Set #$00
        thru
  $000983 Set #$18

Background Music
The track order can be changed in reVamp easily enough, but known values will get posted here. NSF values will not be here... probably. Values get all wonky after using reVamp's Change Tracks function. Will need to test byte values later. Changing more than one or two at a time causes some weird readings in ExamDiff. These pairs are a map, not the music itself.
  $031010 Wallachia
  $031012 Black Forest
  $031014 Causeway
  $031016 Marsh
  $031018 Clock Tower
  $03101A Sunken City
  $03101C Tower of Terror
  $03101E Ship of Fools (2 bytes?)
  $031020 Alucard's Cave
    $AD92 Beginning
    $FD92 Clockwork
    $C192 Mad Forest
    $D592 Stream
    $E992 Dead Beat
    $1193 Aquarius
    $2593 Rising
    $3993 Anxiety
    $4D93 Nightmare

Damage Amounts
This is how much damage enemies and traps do. Damage values start at #$00 for 1 damage.
  $0382E8 Weak attacks (Trevor)
  $0382E9 Normal attacks (Trevor)
  $0382EA Strong attacks (Trevor)
  $0382EE Dull spikes (Trevor)
  $0382F6 Sharp spikes (Trevor)
  $0382F8 Weak attacks (partners)
  $0382F9 Normal attacks (partners)
  $0382FA Strong attacks (partners)
  $0382FE Dull spikes (partners)
  $038306 Sharp spikes (partners)
Damage levels for each enemy are stored in a list. The specific damage level is retrieved by subtracting #$38 from the object_index and then adding #$20 to that value if either Hard Mode is set or the current stage is #$0A (Abandoned Mines) or greater. 
  $02E03D  Damage (R)


Object Index
Only one enemy and one power-up can be stored every 64 pixels horizontally in a horizontal stage. Object indices are found in reVamp by right-clicking on an enemy or power-up in the room editor. Object indices for each room are stored as WORDs, with the lower byte corresponding to the enemy and the upper byte corresponding to the power-up. Don't know why reVamp shows different values than the object index in the room editor.
The index for the object placement maps starts at address $0292BE and is offset simply by stage then block then subroom.
  $0293DE First enemy (1-01:0 far left)
  $0293DF First power-up (1-01:0 far left)
The corresponding value is shifted left to find the address offset for stat map.
  $02A57B Address for power-up stats
Power-up stats are stored as DWORDs, with each byte representing (in order) the luminary type, item dropped, x-coordinate, and y-coordinate.
Luminaries are stored as follows:
    $80 Candle
    $81 Candlestand
    $82 Lantern
  $02A763 Power-up #$00 (Null)
  $02A767 Power-up #$01
         thru
  $02AB2B Power-up #$FF
In vertical stages, enemies and luminaries are hard-coded starting at $02AB2F. The first byte is the screen the enemy or luminary appears in. The second byte is the y-coordinate in that screen. The third value is the enemy type as can be seen in reVamp or the luminary value. The fourth byte is the x-coordinate in the screen. The fifth byte is the item dropped for luminaries, possibly ignored for enemies even though it's set (otherwise bats would drop big hearts). The sixth and seventh bytes aren't used as far as I can tell. A value of $FF in the first byte denotes the end of the list of objects in that vertical room.

Trevor's Starting Coordinates
Trevor's X is (KKKKK & #$F0). Trevor's Y is (KKKKK << 4). Every other byte corresponds to a block. These can be set in reVamp. Good for debugging if $36 is frozen.
  $037802 1-01:0
  $037804 1-02:0
  $037806 1-03:0

Scroll type
Vertical stages have a scroll type specified as #$80 (normal), #$82 (automatic), or #$84 (incremental, like the collapsing towers). When the stage scrolls down, it can take #$81 (normal), #$83 (automatic), or #$85 (incremental, not sure if implemented). You can set this for each room, but if a room isn't set up as vertical, it will fail to load.
  $03DA01 1-01:0 (starting address)
  $03DA03 1-02:1
  $03DA11 2-01:0 Up
  $03DA15 2-02:1 Up
  $03DA18 2-03:1 Up
  $03DA1B 2-03:1 Down
  $03DA1E 2-02:1 Down
  $03DA20 2-01:0 Down
  $03D961 - $3DA00 Scroll type map (and other?)

Prayer Values
These are some of the values set during the prayer scene.
  $00658d Trevor's mirrored state
  $006588 Trevor's x-coordinate
  $00658D Trevor's y-coordinate
  $00667F Trevor's PPU offset
  $006684 Trevor's palette
  $006689 Trevor's "image single"

Doors
Each door has 6 bytes of data. The location of this data is located in a series of WORDs offset by the current stage.
  $01F606-$01F623 PRG-ROM Address (Word) (R)
  $01F624 Door value (R)
    Each of these addresses contains 6 bytes of data, offset by the current block.
    Subroom
    Screen
    Side of room (#$00 = left, #$01 = right)
    First door y-coordinate
    Second door y-coordinate
    Subroom of next block
The first byte tells the game which subroom in the block the door is located. Obviously since there can be only one door per block, there can be only one subroom. The second byte tells the game which screen the door is on. The screen is the higher byte of the View X. The third byte specifies which side of the room the door is on. You can only use one side of the room, not both (CV2 had different screen transitions obviously). The next two bytes specify the y-coordinate Trevor needs to be standing at for either door when walking through. This is how you have two doors per level in the Alucard's cave. And yes, Trevor must be actually standing at that y-coordinate. The final byte tells the game which subroom of the next block to go to.

Stairs
Stairs have quite a bit of code associated with them. The stairs' stats are indexed by stage, block and room. This means adding new stairs is tedious. The indexing is as follows:
    $01F75F Index by stage (Word) (R)
    $01F77D Sub-index by block (Word) (R)
    $01F818 Sub-index by room (Word) (R)
    $01F828 Stair values and breaks (R)
Breaks are included because the game will cycle through all stair values if at any time Trevor's stats don't match those of the currently indexed stair. When a break is encountered, the game stops looking. Stair stats are stored in the format ABCCDD, with each nybble/byte corresponding to the following (coordinates of the reVamp icons are listed below each one):
    A = Direction
        $0 Up and right
            x = left edge
            y = bottom edge + #$10
        $4 Up and left
            x = right edge
            y = bottom edge + #$10

        $8 Down and left
            x = right edge
            y = top edge + #$10
        $C Down and right
            x = left edge
            y = top edge + #$10
    B = Y-coordinate >> 4 or Screen for vertical rooms
    C = X-coordinate or Y-coordinate for vertical rooms
    D = Screen or X-coordinate for horizontal rooms
Putting a solid tile directly under the top of a stair will prevent Trevor from walking down the stair. Climbing stairs makes Trevor ignore tile collisions normally, but if the tile directly below is a solid, the collision will register and he will snap out of the stair to the ledge above.

Special Values
A few stages have special attributes applied to background tiles and are listed in the ROM. The map is very simple. Every DWORD stores (in order of ascending byte) the stage, the block, and the room, then the code for the instructions, which is stored in RAM address $007A.
  $001595 Moving clouds (#$10 to #$13)
  $0015A5 One-way stairs? (#$20 and #$23)
  $0015AD Stream with waterfall (#$30 and #$31)
  $0015B5 Grinding clockwork (#$40)
  $0015E9 Cascading waterfall (#$41)
  $0015F5 Quicksand (#$32 to #$37)
  $00160D Water? (#$50 to #$53)
  $00161D Split room with water? (#$60)
  $001625 Flooding (#$71 and #$72)
  $001629 Collapsing bridge (#$80 and #$81)
  Obviously #$10 thru #$13 handle the values used to reference the instructions for animating background clouds. The lower bits correspond to RAM offsets.
  A value of #$20, I have no idea yet.
  A value of #$23 will make Trevor climb the stairs up to the next block automatically. Like doors, this clears all other instances from the screen.
  When using Sypha, #$30 and #$31 handle water that she can freeze. So no, she can't freeze all water, only the flowing streams with waterfalls in them. These flags also animate the water.
  Values #$40 and #$41 simply handle tile animations. The gears in the Clocktower use #$40 and the waterfalls in the background of the castle tower use #$41.
  The quicksand flag will make every part of Trevor's sprite that is completely under the mud flicker. The lower bits map to $00631A offset by [lower bits]-2. So a value of #$33 would map to $00631B. The values stored within that array correspond to the screen in which no flickering should occur (i.e., the screen with no mud at all). If the corresponding array value is higher than the room size (e.g., $0054 doesn't exceed #$01 but $00631A[n] is set to #$02), the game will render all screens in the room as full of mud. When the array value matches the current screen, no flickering will occur below ground-level at all.
  Not sure if the water flag is actually for water, but seeing as how it's only set in the Sunken City, that's a good sign. It has a similar format to the quicksand flag, but is only used for the lowest subroom. Perhaps Konami was planning something with it. Possibly only used by Fishmen. Both #$50 and #$60 are checked in the same subroutine, which suggests water. Furthermore, the code creates three new objects in the room, but they never appear (at least on my end). This kind of code only occurs when particles are created. In other words, there was probably supposed to be a splash when Trevor hit the water.

Epilogue
Not really something you'll probably ever want or need to change, but if you think it takes too long for the text to start scrolling in the epilogue after the castle crumbles, you can change these values.
  $02B224 Text Delay for Trevor
  $02B225 Text Delay for Sypha
  $02B226 Text Delay for Grant
  $02B227 Text Delay for Alucard
  $02B281 Scroll Speed for Trevor
  $02B282 Scroll Speed for Sypha
  $02B283 Scroll Speed for Grant
  $02B284 Scroll Speed for Alucard
  $02B25A Text Index
The index for the text is referenced by RAM address $0785 and increases with every pass of $078A. When the value retrieved is $FF, the text stops loading and scrolls to the top of the page. The three or four indices before the $FF are typically void of text so the epilogue scrolls off the screen before ending.


Enemy Spawner
Enemies are not directly placed in the room, but rather a spawner is. There can only be 6 spawners loaded at any one time (within 64px blocks as seen in reVamp). Each spawner holds an index to the code snippet that handles spawning the enemy. The program will check the object_index stored in each RAM offset from $054E-$0556. When a match with the designated object_index is found, $000E is incremented. Upon verifying each object_index, it compares $000E against the value stored in $000D (which is hardcoded as #$03). If $000E<$000D, it looks for the first RAM offset without an object_index. Some objects are forcefully set to a higher range. The program then clears all the preset RAM offsets within the current X register's range. Next, it sets the x- and y-coordinates, the object_index, and whatever $05EF is. It then retrieves the enemy's health and damage.
  $028DD2  Multiple Object Limit
  $028533  Offset
Each step the game will retrieve the spawner's offset value and retrieves an address. It then takes the spawn count and uses it to retrieve another address offset from the first address then executes the code there. If no enemy exists, this usually jumps to $8B90, otherwise it goes to $8BB0, I think. Script $8BB0 simply updates the position of the spawner.
For the most part,  spawner data can be edited in reVamp by right-clicking on a spawner in the room. The data there is found between ROM addresses $2A13E and $2A56A. The first value is the spawner type. The Second value is the x-offset from every 64-pixel block. The third value is the y-offset. The fourth and fifth values are special values for enemies or spawners that need them (e.g., Ghosts, Fuzzbusters, Harpies, Bone Dragons, Bone Pillars, Crows); the fourth byte is for RAM offset $07E6 and the fifth byte is for RAM offset $07CE

 

Respawn Conditions
Some enemies can be specified to respawn or perform other actions when slain.
  $02F553  #$4B
  $02F557  #$47
  $02F55B  #$49
  $02F55F  #$4D
  $02F563  #$38
Some have different displays when slain. 
  $02F53B  #$3D
  $02F53F  #$3E
  $02F543  #$4B
  $02F547  #$47

Collision Formula
The formula for horizontal collisions is
  abs(ALLY.x-OTHER.x)<=(ALLY.hbound+OTHER.hbound)
The formula for upper vertical collisions is
  ALLY.y+ALLY.vbound - (OTHER.y-OTHER.vbound)<#$12

Bounding Box Offsets
Using the object IDs below as Other pointers
  $02F683  Ally Vertical
  $02FB15  Ally Horizontal
  $02FB90  Other Horizontal
  $02FC18  Other Vertical

Primary Object IDs
$01  Skull Knight
$02  Cyclops
$03  Grant
$04  Giant Bat
$05  Alucard Bat / Cape
$06  Bone Dragon King
$07  The Monster
$08  Moat Dragon
$09  Triad Wisp / The Devil
$0A  Medusa
$0B  Doppelganger 
$0C  Death
$0D  Dracula
$0E  Mummy Boss 
$0F  Doppelganger Weapon
$12  Storm Clouds
$13  Small Lightning 
$14  Grant's Knife
$15  Grant's Axe
$16  Soul Shard 
$17  Alucard Fireball
$1A  Boss Death Effect
$1F  Cyclops' Killer Lightning?
$20  Timer for Cyclops' Lightning?
$21  Alucard Head
$23  Devil's Fireball
$24  Dracula's Pyre
$25  Dracula's Head
$27  Mummy Boss Wrap
$29  Legion's Drool / Pazuzu's Laser
$2B  Scythe
$30  Normal Fireball
$31  Axe 
$32  Teardrop 
$33  Bone
$34  Mummy Wrap
$35  Spiderling 
$36  Sporeling 
$37  Embers
$38  Zombie
$39  Crow 
$3A  Bats
$3B  Medusa Head
$3C  Ghost
$3D  Skeleton
$3E  Skeleton (Whip)
$3F  Floating Eye
$40  Spore Float
$41  Winged Demon
$42  Hunchback 
$43  Slime 
$44  Skeleton (Sword)
$45  Axe Knight
$46  Bone Pillar
$47  Blood Skeleton (Whip) 
$48  Merman
$49  Bone Dragon
$4A  Mummy 
$4B  Blood Skeleton
$4C  Dhuron
$4D  Spider 
$4E  Spore Bloom
$4F  Owl 
$50  Mudman
$51  Frog
$52  Fireman
$53  Knight
$54  Fuzzy
$55  Harpy
$58  Spiderweb / Crumbling Mummy
$61  6-Tile Current
$62  2-Tile Current(1)
$63  Auto-Walk (Caves)
$64  Auto-Walk (Forest)
$65  2-Tile Current (2)
$66  4-Tile current
$68  Normal Lightning
$69  Collapsing Walkway
$6A  Teeter-Totter
$6B  Falling Block Spawner
$6C  Water Droplet Spawner
$6D  Trap Door
$6E  Spiked Platform
$6F  Clock Pendulum
$70  Gear Teeth
$72  Spiked Trap Door
$73  Water Droplet/Falling Block
$74  Spike Crusher
$75  Medium Gear
$76  Vertical Platform
$77  Horizontal Platform 
$78  Scrolling Platform
$7A  Pazuzu Platform
$7B  Floating Platform
$80  Candle
$81  Candlestand
$82  Lantern

Enemy Subroutines
$01  Zombie (from side, slow or fast[2])
$02  Zombie (from ground)
$03  Crow (low)
$04  Crow (high)
$05  Bat (flying[2])
$06  Bat (sleeping) 
$07  Medusa Head
$08  Ghost (no flicker)
$0B  Floating Eye 
$0C  Spore Float
$0D  Winged Demon
$0E  Hunchback 
$0F  Slime 
$10  Skeleton (sword)
$11  Axe Knight
$12  Bone Pillar (3-shot[1])
$14  Fishman (Jump only)
$16  Mummy 
$19  Crumbling Mummy
$1C  Dhuron
$1D  Spider
$1E  Bone Pillar (2-shot) 
$22  Spore Bloom
$25  Mudman
$26  Frog
$27  Fishman (Swim only)
$29  Fishman (Swim & Jump)
$2B  Knight 
$2C  Bone Dragon Head
$2D  Bone Dragon Rib
$2E  Bone Dragon Base
$2F  Bone Pillar (3-shot[2])
$38  Zombie (from side, fast[1])
$57  Spiderweb
$58  Fireball
$59  Axe 
$5A  Teardrop
$5C  Mummy Wrap
$5D  Spiderling
$5E  Sporeling 
$5F  Embers
$63  Owl 
$64  Fuzzy
$66  Bat (flying[1])
$68  Ghost (flicker)


Sound Files
These are the values sent to the CPU for sound files via address $E249.
SFX
  $01  High Snare Hit
  $02  Hi-Hat Shut Hit
  $03  Hi-Hat Open/Ride Cymbal Hit
  $04  ****UNKNOWN NOISE****
  $05  Low Snare Hit
  $06 [U:$07]  Crumbling Room
  $07 [U:$09]  Footsteps
  $08 [U:$0B]  Rough Landing
  $09 [U:$0C]  Door Slam  
  $0A [U:$0D]  Bouncing Slime Landing
  $0B [U:$0E]  Giant Rotating Gear
  $0C [U:$0F]  Mudman Appearance
  $0D [U:$10]  Crumbling Ledge 
  $0E [U:$08]  Corrosive Water Corrosion
  $0F [U:$11]  Ceiling Smash | Ledge Fall
  $10 [U:$12]  Crumbling Bridge
  $11 [U:$13]  Axe Weapon Toss
  $12 [U:$14]  Dagger Toss
  $13 [U:$15]  Cross Toss
  $14 [U:$16]  Holy Water Shatter
  $15 [U:$17]  Invincibility Potion
  $16 [U:$18]  Get Coins
  $17 [U:$19]  Timer Tally 
  $18 [$U:1A]  Hearts Tally | Name Letter Select
  $19 [U:$1B]  Get Heart | Name Letter Enter
  $1A [U:$1C]  Get Weapon
  $1B [U:$1D]  ****UNKNOWN****
  $1C [U:$1E]  Water Attack (Lightning in v.US)
  $1D [U:$1F]  Alucard Fireball
  $1E [U:$20]  Flowing Water
  $1F [U:$21]  Ice Spell  
  $20 [U:$22]  Emerge Splash
  $21 [U:$23]  Submerge Splash 
  $22  Corrosive Water Splatter
  $23 [U:$24]  Fire Spell (for Water Dragons also)
  $24  Resilient Enemy Hit 
  $25  Roaring Waterfall
  $26  Owl Flap
  $27  Enemy Shattered (e.g., skeletons)
  $28  Ineffective Attack 
  $29  Cyclops Pound
  $2A  Boss Hit
  $2B  Mystery Meat 
  $2C  Thunder
  $2D  Title Screen Thunder
  $2E  Bat Form
  $2F  Water Dragon Emerge
  $30  Water Dragon Submerge
  $31  Bone, Spit, Tears, et al Attack
  $32 [U:$33]  Object Destroy
  $33  Block Break 
  $34  River Freeze
  $35  Teeter-Totter (removed)
  $36  Trap Door Turn 
  $37  Collapsing Tower | Leviathan Stomp
  $38  Frozen Enemy Shattered
  $39  Creature Stomp
  $3A  Medusa Beam (removed)
  $3B  Medusa Arrow (removed)
  $3C  Clocktower Quake
  $3D  Sunken Room Quake
  $3E [U:$3C]  Stopwatch Tick
  $3F  Flooding Sunken Room
  $40  Prayer Thunder
  $41  Big Thunder
  $42  Invalid Password
  $43  Partner Saved
  $44  Flame Pillar
  $45  Wisp Explode
  $46  Pazuzu Laser
  $47  Doppelganger Change
  $48 [U:$46]  Partner Change
  $49  Pazuzu Hit
  $4A  Crystal Ping
  $4B  Time's Up
  $4C  Rosario
  $4D [U:$4B]  1UP
  $4E [U:$4C]  Health Refill
  $4F [U:$4D]  Pause  
  $50 [U:$4E]  "Life Loss"
  $51 [U:$4F]  "Beginning"
  $52 [U:$50]  "Mad Forest"
  $53 [U:$51]  "Stream"
  $54 [U:$52]  "Dead Beat"
  $55 [U:$53]  "Clockwork"
  $56 [U:$54]  "Aquarius"
  $57 [U:$55]  "Rising"
  $58 [U:$56]  "Anxiety"
  $59 [U:$57]  "Nightmare"           
  $5A [U:$58]  "Demon Seed"          
  $5B [U:$59]  "Anxiety" (duplicated)
  $5C [U:$5A]  "Aquarius" (duplicated)
  $5D [U:$5B]  "Deja Vu"
  $5E [U:$5C]  "Riddle"
  $60 [U:$5E]  "Overture"
  $61 [U:$5F]  "Boss Fight"
  $62 [U:$60]  "Big Battle"
  $63 [U:$61]  "Big Battle" (fast)
  $64 [U:$62]  "Epitaph"
  $65 [U:$63]  "Boss Clear"
  $66 [U:$64]  "All Clear"
  $67 [U:$65]  "Game Over"
  $68 [U:$66]  "Prelude"
  $69 [U:$67]  "Prayer"
  $6A [U:$68]  "Evergreen"
  $6B [U:$69]  "Flash Back"
  $6C [U:$6A]  "Pressure"
  $6D [U:$6B]  "Encounter"
  $6E [U:$6C]  "Destiny" 
  $6F  Floor Tom (DPCM)
  $70  Low Tom (DPCM)
  $71  High Tom (DPCM)
  $72  Snare Drum (DPCM)
  $73  Bass Drum (DPCM)
  $74 [U:$72]  Attack / Main Menu Select
  $75  Trevor Hurt
  $76  Grant Hurt
  $77 [U:$75]  Sypha Hurt
  $78  Alucard Hurt
  $79  Death Laugh (DPCM)
  $7A  Whip Attack (duplicated)
  $7B  Ominous Laugh (DPCM)
  $7C  Flying Heads Scream (DPCM)
  $7D  Boss Scream (DPCM)


Constants
As I find them, I will include the constants (enemy stats, timer durations, etc.) here. Addresses identified as offsets should only be modified with extreme caution.
  $000F42  Starting Hearts
  $000F3D  Starting Lives
The above two can be easily changed in reVamp.
  $03BA3D  Stopwatch Duration
Default is #$B4, which is 180 steps. In other words, it's 3 seconds if running at 60 fps. Oddly, the timer requires 64 steps to count down 1 second, which I've noticed in other games as well.
  $02925E  Enemy Health (R)
Every enemy's health is stored in this range, sorted by object index. Every boss has a unique object index, which means bosses can have different health, but anything higher than #$40 will not register properly in the boss' health bar at the top of the screen.
  $013FA0  Point Value (R)
  $02C3E8  Byte $05AA (R)
The offset is retrieved by object_index-#$38. This is tripled and used as a sprite offset.
Hit detection is performed in Begin Step event (essentially). 
Sleeping Bat
  $02C7C0  Integral vertical speed ascending
  $02C7C8  Fractional vertical speed ascending
  $02C898  Integral vertical speed descending
  $02C89A  Fractional vertical speed descending
  $02E7AF  PPU address
  $02E7B0  Image single
  $02E7B2  Offset for proximity to awaken
  $02E7B3  Horizontal proximity to awaken
  $02E7B4  Vertical proximity to awaken
  $02E7B6  Offset for initialization subroutine
  $02E7B7  Integral horizontal speed when waking
  $02E7B8  Fractional horizontal speed when waking
  $02E7BA  Offset for flying down
  $02E7BB  Offset for vertical speed down
  $02E7BC  Timer (for when to change direction)
  $02E7BE  Offset for timer decrease
  $02E7BF  Vertical speed deceleration
  $02E7C2  Offset for flying up
  $02E7C3  Offset for vertical speed up
  $02E7C4  Ystart augment when ascending
  $02E7C6  Offset for sinusoidal movement up
Bone-Tossing Skeleton
  $02CFBD  Bone object index
  $02CFC5  Bone y relative to skeleton's y
  $02CFCD  Bone $05EF,X
  $02CFD9  Bone x relative to skeleton's x
  $02CFE9  Bone horz_3 (offset with xscale)
  $02CFF9  Bone horz_2 (offset with xscale)
  $02D009  Bone vert_3 (offset with xscale)
  $02D019  Bone vert_2 (offset with xscale)
  $02D439  Integral horizontal speed walking
  $02D43D  Fractional horizontal speed walking
  $02E932  Offset for Phase 0
  $02E936  Offset for Phase 1
  $02E933  Integral horizontal speed  
  $02E934  Fractional horizontal speed
  $02E936  Offset for setting timer
  $02E93A  Offset for Phase 2 
  $02E93E  Offset for Phase 3
  $02E93F  Value for setting alarm jumping
  $03E943  Offset for Phase 4
  $03E946  Offset for Phase 5
  $02E947  PPU address tossing
  $02E948  Sprite offset tossing
  $02E94A  Offset for Phase 6
  $02E94B  Value for setting alarm tossing 
  $02E94E  Offset for Phase 7 
  $02E952  Offset for Phase 8
  $02E956  Offset for Phase 9
  $02E95A  Offset for Phase 10
  $03F0F6  Image single walking
  $03F0F7  Image speed walking
  $03F0F8  Max image index walking
  $03F12C  Image single tossing
  $03F12D  Image speed tossing
  $03F12E  Max image index tossing
Ghost 
  $02D940  Integral horizontal speed (Normal mode)
  $02D942  Integral horizontal speed (Hard mode)
  $02D944  Fractional horizontal speed (Normal mode)
  $02D946  Fractional horizontal speed (Hard mode)
  $02D948  Integral vertical speed
  $02D94A  Fractional vertical speed
  $02E8BF  PPU Address
  $02E8C0  $5AA,X
  $02E8E6  Offset for Phase 10
  $02E8E8  Alarm until checking position
  $02E8EA  Offset for Phase 11
  $02E8EE  Offset for Phase 12
  $02E8F2  Offset for Phase 13
  $02E8F3  Loop point
  $03F152  Max image index 
Crow
  $02C449  PPU address
  $02C44D  Sprite offset
  $02D6F8  Vertical proximity 
  $02D714  Phase 3 alarm settings (R)
  $02D735  Phase 4 alarm settings (R)
  $02EAFE  Offset for Phase 0
  $02EB02  Offset for Phase 1 
  $02EB03  Horizontal proximity to attack
  $02EB04  Vertical proximity to attack
  $02EB06  Offset for Phase 2
  $02EB0A  Offset for Phase 3 
  $02EB0E  Offset for Phase 4
  $02EB12  Offset for Phase 5
  $03F0EB  Image speed
  $03F0EC  Max image index
Hunchback
  $02C3E1  PPU Address
  $02C3F2  $5AA,X 
  $02C627  Horizontal proximity to attack
  $02C64C  Vertical acceleration (hop)
  $02C651  Integral vertical speed (hop)
  $02C653  Fractional vertical speed (hop)
  $02C658  Integral horizontal speed (hop)
  $02C65A  Fractional horizontal speed (hop)
  $02E766  Offset for Phase 2
  $02E76A  Offset for Phase 3 
  $02E76B  Alarm before attacking
  $02E76E  Offset for Phase 4
  $02E772  Offset for Phase 5
  $02E776  Offset for Phase 6
  $02E777  PPU address (hop)
  $02E778  Image single (hop)
  $02E77A  Offset for Phase 7
  $02E77E  Offset for Phase 8
  $02E77F  PPU address (land)
  $02E780  Image single (land)
  $02E782  Offset for Phase 9
  $02E783  Alarm before attacking again
  $02E786  Offset for Phase 10
  $02E78A  Offset for Phase 11
  $02E78B  Loop point
  $02F7AD  Horizontal bounds for collision in front
  $02F7AF  Horizontal bounds for collision below
  $02F7B1  Horizontal bounds for collision above  
  $02F7D3  Vertical bounds for collision in front
  $02F7D5  Vertical bounds for collision below
  $02F7D7  Vertical bounds for collision above
  $03F102  Image single (idle)
  $03F103  Image speed (idle)
  $03F104  Max image index (idle)
Whip Skeleton
  $02FB15  Horizontal bounds
  $02FB1E  Vertical bounds
  $02FB40  Whip length
  $02FB48  Whip height
  $02FB50  Whip collision reach
  $02FB60  Whip collision thickness
  $02FBCE  Trevor's horizontal bounds
  $02FC56  Trevor's vertical bounds
      $02FB50 + skeleton.x - Trevor.x < ($02FB15 + $02FB40)

      $02FB60 + skeleton.y - (Trevor.y+$02F4A4) < ($02FB1E + $02FB48)
Death
  $00D9F9  Scythe limit


Notes To Self

$037724 (50) (7C & $F0 3A)

$3D909 (01 80) address for climbing up stairs to next room based on $0034
next address is $3D909 + $0035 << 1 offset, add #$18010 to find ROM address
0180 0
E28D 1
AF99 2
82A6 3
11B3 4
0180 5
FF89 6
6F91 7
DE9D 8
0180 9
1088 A
0EAA B
CB9F C
4BA9 D
B7B2 E
Above address offset by $0035 << 1

$038613 (R) Map to Trevor's x-coordinate offset when changing rooms via stairs
$038614 (R) Map to Trevor's y-coordinate when changing rooms via stairs
$03862B (R) Map to Trevor's y-coordinate offset (?) based on $054E and additional x-coordinate offset based on $05EF (whatever that is), usually +0

Y-values in reVamp vary from game values by 1 whole tile height as follows:
yrevamp = ygame - #$20{status bar} + #$10
When height checked uses that formula, collision is for at instance's feet. Discrepancy shouldn't ever be more than #$10 or less than #$F0 (above head).
Collisions in front of objects are checked 1 whole tile width (#$10) ahead.

These are the "hit box" settings for tile collision of various objects:
Trevor
In my engine, Trevor's y is $10 pixels higher than in the actual game, so y+$10-$20, $20 being the height of the status bar, in my engine would be y+$20 (I think).
(x±8,y±16) Wall collision
( x±5,y+16) Floor collision
(x,y-8 6r y-24) Jumping

( $800C + #$09 + $0036 << 1 + #$01 ) >> #$04 = next subroom when ascending from vertical
x($0A)+#$0C = AB; A = next subroom << 4, B = next screen
x($0A)+$0036 = BG palette offset or palette offset+#$1C

$9378 Trevor's Bounding box addressing
Indexed by $9375+$0565+1
2D95 $02
6796 $04
2496 $06
7797 $08
2099 $0A
7797 $0C
5799 $0E
6B99 $10
A499 $12
AB9A $14
4999 $16
0D94 $18
2F94 $1A
5A94 $1C
9394 $1E
AD94 $20
C994 $22
F494 $24
0783 $26
A693 $28
A693 $2A
588B $2C
DF8A $2E

view_x&$3F[0E]&$20+$C0[09] if ($0062)==0 else view_x&$3F&$20+$00
($0073)+$05(*$0062>0)[73]
$01[0A]
$8410,73 (enemy block)


Interactive Terrain (QWord)Moving objects between screens sometimes glitches in reVamp.
  $00A030  Index 4 (Object Map)
  $00A054  Index 1 (Word Map)
  $00A0F2  Index 2 (Offset Map)
  $00A17A  Index 3 (Stats Map)
A  B  C  D  E  F  G  H
02 E8 00 10 50 00 01 00
Breakable Block 
  A  Screen  
  B  X-coordinate (Y in vertical stages)
  (#$8 right from left edge)
  D  Object (#$10;#$11 in vertical stages)
  (used when loading into room)   E  Y-coordinate (X in vertical stages)
      (#$D down from top edge; subtract 8 if G set)
  F  Item  
      ($00=Meat, $01=Heart, $02=Empty, $03=Multiplier, $04=1UP)
  G  Dual Layer
  H  Instance ID (counter)
Horizontal Ledge
  C  Screen Trigger 
      (see reVamp)
  D  Object (#$0C)
  G  Velocity 
      (see reVamp)
      Minimum is #$01. Setting the highest bit moves ledge left.
  H  Range (see reVamp)
Vertical Ledge
  D  Object (#$0B)
  F  Range 
      (see reVamp)
  G  Velocity 
      (see reVamp)
      Minimum is #$01. Setting the highest bit moves ledge up.
Moving Spikes /Crusher
  D  Object (#$06;#$07)
  F  Up-Down State?
  G  Range 
      (see reVamp)
      Values in reVamp don't match values in ROM. Huge variance.
Trap Doors
  D  Object (#$02;#$03)
  F  Up-Down State?
  G  Location 
      (see reVamp)
      Not sure why this is used.
Pendulum
  D  Object (#$05)
  F  Location 
      (see reVamp)
  G  Velocity 
      (see reVamp)
      Positive for left, negative for right. 
Gears
  C  ??
  D  Object (#$0A;#$04)
  F  Direction 
      Clockwise=#$00; Counterclockwise=#$01)
   G  Location 
      (see reVamp)
Tilting Ledge
  D  Object (#$01)
  F  Location 
      (see reVamp)
  G  Tilt 
      L-tilt should be #$01, but this seems inconsistent.
Falling Blocks
  D  Object (#$08)
  F Location 
      (see reVamp)
Acid Drops
  D  Object (#$09)
  F  Location 
      (see reVamp)
Scrolling Ledges
  B  ??
  C  ??
  D  Object (#$0D)
  H  ??


Breakable Blocks
Breakable blocks occupy X offsets #$1A and #$1B.


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