Data
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31241: Per-screen RAM state
First 26 bytes of the runtime RAM map. The remaining per-game-state scratchpad variables live further down in the code segment near 33682 — see that block for the rest of the RAM map.
Variables:
Variable Meaning
DrawSlotIndex actor slot (0-7) currently drawn/processed
CurrentRoom room of that actor; "the viewed room"
RoomTypeByte view type: deck 0-2 of ShipMapData, 3 = Narcissus, 4 = alien-encounter screen
RoomAttrStep word: attr-cursor stride for door drawing
RoomCellStep word: cell-grid stride for door drawing
HeldItemFront item id in the actor's front hand (255 = none)
HeldItemBack item id in the actor's back hand (255 = none)
RoomMateA first other actor in the room (255 = none)
RoomMateB second other actor in the room (255 = none)
RoomModeByte current room mode (drives RoomDispatchTable)
ShipSystemFlags bit 0 destruct armed; bits 1/2 airlocks blown; bits 3-5 engine state
RoomAttrCursor word: attribute-file cursor (room drawing)
DrawScreenPtr word: THE display-file draw pointer (~120 refs)
RoomCellCursor word: 20-wide room-cell-grid cursor
CorridorTilePtr pointer into corridor tile source
CrewAnimFlags XOR-blit toggle for crew sprite set A
AnimFramePhase XOR-blit toggle for set B / cursor
ScriptPointer ROM-traversal AI script pointer
The bytes from 31267 onwards hold executable code (the view background renderer, invoked via CALL 31267 from 31459 and 32719), preserved as DEFB data only because the section was originally classified as RAM.
Decoded, DrawRoomBackground reads: fill the 20x19 attribute window with 4 (green ink); A = RoomTypeByte; if A = 3 JP NarcissusBackground; if A = 4 JP ResetAlienXAnim (the encounter screen); else HL = ShipMapData + 380*A (that deck's 20x19 tile map) and fall into DrawRoomBackground_0, which renders the 20x19 tile map at HL onto the display via DrawSpriteRow — also called directly by NarcissusBackground with the RLE-expanded grid buffer.
31241 DEFB 5
31242 DEFB 6 room of the actor being processed (record byte +1, cached by SelectSlotByDrawIdx); doubles as "the viewed room" in encounter checks
31243 DEFB 1
31244 DEFB 0,0 word: attribute-cursor stride for door drawing
31246 DEFB 0,0 word: room-cell-grid stride for door drawing
31248 DEFB 255 corridor-strip cell (0-21) of the actor's id+160 marker; 12 = the alien's lair cell (see 31823)
31249 DEFB 255 corridor-strip cell of the actor's id+128 marker
31250 DEFB 255 slots of up to two OTHER actors in the current
31251 DEFB 255 room (255 = none) - printed as "Also here" / "Also Bodies of"; found by 36187
31252 DEFB 0
31253 DEFB 0 bit 0 = self-destruct armed; bits 1/2 = Airlock #1/#2 blown open (set by BlowLock, cleared by SealLock); bits 3-5 = Engine #1/#2/#3 state (ship-systems tick at 39041)
31254 DEFB 0
31255 DEFB 0,88 word: attribute-file cursor for room/door drawing (initially the attr-file base)
31257 DEFB 0,64 word: THE main display-file draw pointer used by every blit routine (initially the display file)
31259 DEFB 0,96 word: cursor into the 20-cell-wide room grid, walked in step with RoomAttrCursor
31261 DEFB 0,0
31263 DEFB 128
31264 DEFB 128
31265 DEFB 0,0
31267 DEFB 17,12,0,33,0,88,14,19
31275 DEFB 6,20,54,4,35,16,251,25
31283 DEFB 13,32,245,17,124,1,33,0
31291 DEFB 96,58,11,122,254,3,202,108
31299 DEFB 131,254,4,202,7,155,167,40
31307 DEFB 4,25,61,32,252
31312 DEFB 34,27,122,33,0,64,34,25
31320 DEFB 122,14,19,6,20,197,237,91
31328 DEFB 27,122,205,137,122,33,25,122
31336 DEFB 52,42,27,122,35,34,27,122
31344 DEFB 193,16,234,17,12,0,42,25
31352 DEFB 122,125,254,224,56,3,17,12
31360 DEFB 7,25,34,25,122,13,32,211
31368 DEFB 201
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