Fairlight: Game status buffer entry at FF80

IY holds OBJECT_COUNT throughout the game, so most of these are reached as IY+n: the author's source text calls this base V, as in (V+3), and the listing writes each such access the same way, as the variable less V: (IY+ROOM-V) is ROOM, and V is an EQU at the top of the source file. Only two places move IY: ZOOMIN (ZOOMIN) points it at a chaser's target for a moment, and ROOMST steps it through the carried things. On the tape the first 61 bytes, up to OBJECTS_PLACED, hold the values a game starts with; the start-up copies them to the master copy (MASTER_OBJECTS) and a new game copies them back. The rest are set before they are read; on the tape many hold the ends of the ROM's user-defined graphics, like UDG_LEFTOVERS.

From POINT up the bytes have several lives, one at a time. While a room is drawn they are the drawing's state, twenty of them (from ORIGIN) reset from ROOM_DEFAULTS for each room. While an object is updated (CHE3D), POINT to WORK_HEADING are a copy of its record's first 19 bytes -- the author's T, as in (T+13) -- so that IY+$64 is the record's +0, IY+$6A its x (+6), IY+$6B its y (+7), IY+$6C its z (+8), IY+$70 its kind (+12) and so on; FOUND_RECORD (T+20), STEP_AXES, ASKED_DIRECTION, WORK_RECORD and RIDE_DIRECTION go with them. While a sprite is drawn (REDRAW_OBJECT) the same bytes hold the rectangle being redrawn, from a copy of +0 to +11, and the drawing's counters; and DRAW_LIST, lower down, takes a list of 30 bytes that runs over the printer's and the room drawing's bytes. Each use sets what it reads first.

The labels are for the use the object code makes of a byte where it reads it by address, and for the drawing's otherwise.

IY holds OBJECT_COUNT throughout the game, so most of these are reached as IY+n: the author's source text calls this base V, as in (V+3), and the listing writes each such access the same way, as the variable less V: (IY+ROOM-V) is ROOM, and V is an EQU at the top of the source file. Only two places move IY: ZOOMIN (ZOOMIN) points it at a chaser's target for a moment, and ROOMST steps it through the carried things. On the tape the first 61 bytes, up to OBJECTS_PLACED, hold the values a game starts with; the start-up copies them to the master copy (MASTER_OBJECTS) and a new game copies them back. The rest are set before they are read; on the tape many hold the ends of the ROM's user-defined graphics, like UDG_LEFTOVERS. From POINT up the bytes have several lives, one at a time. While a room is drawn they are the drawing's state, twenty of them (from ORIGIN) reset from ROOM_DEFAULTS for each room. While an object is updated (CHE3D), POINT to WORK_HEADING are a copy of its record's first 19 bytes -- the author's T, as in (T+13) -- so that IY+$64 is the record's +0, IY+$6A its x (+6), IY+$6B its y (+7), IY+$6C its z (+8), IY+$70 its kind (+12) and so on; FOUND_RECORD (T+20), STEP_AXES, ASKED_DIRECTION, WORK_RECORD and RIDE_DIRECTION go with them. While a sprite is drawn (REDRAW_OBJECT) the same bytes hold the rectangle being redrawn, from a copy of +0 to +11, and the drawing's counters; and DRAW_LIST, lower down, takes a list of 30 bytes that runs over the printer's and the room drawing's bytes. Each use sets what it reads first. The labels are for the use the object code makes of a byte where it reads it by address, and for the drawing's otherwise.
OBJECT_COUNT	FF80	DEFB $00	Records in use, counted from FIXED_RECORDS: the six fixed ones, the knight's (7), then the carried things' and the room's
	FF81	DEFB $02	Not used
STRIKES_AT	FF82	DEFB $0B	The low byte of the strike counter of the fighter FIND_OBSTACLE last passed ($98 to $9D)
THIS_RECORD	FF83	DEFB $00	The number of the record being updated or drawn, counted from FIXED_RECORDS (the knight is 7)
	FF84	DEFB $80	Not used
GRAVITY	FF85	DEFB $23	$23, never written: its top six bits are ORed into the direction of a thing not rising -- bit 5, down (ANIMATE_AND_MOVE)
OPTIONS	FF86	DEFB $10	Bit 3: the Kempston joystick is in use (9 turns it on and off)
MESSAGE	FF87	DEFB $00	The message SHOW_MESSAGE is to show: 1 BLOCKED, 2 LOCKED, 3 TOO HEAVY; 0 none
MESSAGE_TIMER	FF88	DEFB $00	MESSAGE_TIMER: passes the message stays up (10). Then two bytes not used; NO_RISE_MASK (IY+NO_RISE_MASK-V), $EF and never written: ANDed with the direction of a thing not rising, it takes out bit 4, up (ANIMATE_AND_MOVE); and two more not used
	FF89	DEFB $00
	FF8A	DEFB $00
NO_RISE_MASK	FF8B	DEFB $EF
	FF8C	DEFB $00
	FF8D	DEFB $00
ROOM_COLOUR	FF8E	DEFB $00	The room's colour, from its first byte
DECOY	FF8F	DEFB $00,$00	The record of a decoy (kind 8) in the room, noted by CHE3D for the guards of behaviour 9
THINGS_NOTED	FF91	DEFB $00	Bit 0: a decoy is in the room (DECOY); bit 1: a thing of kind 11 is, which wakes the creature of behaviour 15 and lets the doors of room 61 be used (CHE3D, BUMPED)
CARRIED_WEIGHT	FF92	DEFB $00	The weight of what is carried; 8 or more is too heavy
	FF93	DEFB $00	Not used; then FALL_COUNT (IY+FALL_COUNT-V), the passes the knight has been falling: each over 20 costs 1 LIFE when he lands (CREATURE_UPDATE; measured in the simulator)
FALL_COUNT	FF94	DEFB $00
LIFE_TENS	FF95	DEFB $09	LIFE: the tens
LIFE_UNITS	FF96	DEFB $09	LIFE: the units
GAME_FLAGS	FF97	DEFB $00	Bit 0: LIFE to be printed; 1: the knight's sword out; 2: the room's first pass; 3: the knight's idle pose; 4: still things being drawn into the room; 6: a message showing; 7: the creatures frozen
STRIKES_LEFT	FF98	DEFB $00,$3E,$08,$08,$08,$08	Six fighters' strikes left, 4 each when a room is entered (FIND_OBSTACLE deals them out)
SELECTED	FF9E	DEFB $9F	The low byte of the word in CARRIED for the thing in use ($9F to $A7)
CARRIED	FF9F	DEFB $00,$00	The records of the five things carried
	FFA1	DEFB $00,$00
	FFA3	DEFB $00,$00
	FFA5	DEFB $00,$00
	FFA7	DEFB $00,$00
	FFA9	DEFB $44,$48,$70,$48,$44,$42,$00,$00	Not used
	FFB1	DEFB $40,$00,$00	Not used
ROOM	FFB4	DEFB $1D	The room the knight is in
PARTS_TABLE	FFB5	DEFB $8C,$75	Where the parts are (PART1)
	FFB7	DEFB $00	Not used
FREE_RECORD	FFB8	DEFB $00,$00	The next free object record
OBJECT_TABLE_AT	FFBA	DEFB $24,$A9	Where the object table is (OBJECTS)
OBJECTS_PLACED	FFBC	DEFB $42	Bit 0: the object table's things have been placed in this room (room code $E4, MORE_ROOM_COMMANDS); the rest not used
	FFBD	DEFB $42
	FFBE	DEFB $42
	FFBF	DEFB $00
	FFC0	DEFB $00
	FFC1	DEFB $42
	FFC2	DEFB $62
	FFC3	DEFB $52
	FFC4	DEFB $4A,$46	Not used
DRAW_LIST	FFC6	DEFB $42	30 bytes to the end of AWAY_FRAMES: the numbers of the records to draw, in order, copied from BUFFER_DA00 by SORT_AND_DRAW_BEHIND
	FFC7	DEFB $00,$00,$3C,$42	More of DRAW_LIST
ARRIVAL_BOX	FFCB	DEFB $42,$42,$42,$3C,$00	The door code (BUMPED) points IX here, so that a record's +5 to +11 are PRINT_X and the six bytes after it: the box of a door's far side
PRINT_X	FFD0	DEFB $00	Where the next character is printed: x
PRINT_Y	FFD1	DEFB $7C	And y
	FFD2	DEFB $42,$42,$7C,$40,$40,$00,$00,$3C	The rest of ARRIVAL_BOX, and more of DRAW_LIST
PLACED_TYPE	FFDA	DEFB $42	The type of the object being placed (PLACE_OBJECT)
PLACED_NUMBER	FFDB	DEFB $42	Counts the object table's entries as PLACE_ROOM_OBJECTS walks it: the number it gives a record at +$13 (it wraps round after 255)
	FFDC	DEFB $52,$4A,$3C	More of DRAW_LIST
ORIGIN	FFDF	DEFB $00	Added to x (+6) of each object the room places (IY+$5F-$61; room code $E4 $05)
ORIGIN_Y	FFE0	DEFB $00	Added to its y, the height (+7)
ORIGIN_Z	FFE1	DEFB $7C	Added to its z (+8)
AWAY_FRAMES	FFE2	DEFB $42,$42	How far the knight's frames for walking away (+x or +z) lie beyond those for walking towards the viewer, set just before FACING adds it
POINT	FFE4	DEFB $7C	The room drawing's first point: column. While an object is updated, its +0; in ROOMST, where the next carried record goes
POINT_ROW	FFE5	DEFB $44	And row. While an object is updated, its +1
SECOND_POINT	FFE6	DEFB $42	The second point: column. While an object is updated, its +2
SECOND_POINT_ROW	FFE7	DEFB $00	And row. While an object is updated, its +14 as it was when the update began (CHE3D)
WORK_SPRITE	FFE8	DEFB $00	While an object is updated or drawn, its sprite (+4, +5, a word); zero, and the byte the screen is cleared with, when a room is drawn (CLEAR_ROOM_SCREEN)
	FFE9	DEFB $3C	The sprite's high byte; then LINE_PAGE (IY+LINE_PAGE-V): 0 to draw a room's lines on the screen, $80 in the clean copy (room code $E4), and while an object is updated, its x (+6)
LINE_PAGE	FFEA	DEFB $40
MODE	FFEB	DEFB $3C	The room drawing's mode bits (room codes $C1-$CE, $E4 $04); while an object is updated, its y (+7)
REPEATS	FFEC	DEFB $02	How many times the room drawing repeats (room code $D5); while an object is updated, its z (+8)
	FFED	DEFB $42	Kept with REPEATS by room code $E1; while an object is updated, its x length (+9)
REPEAT_FROM	FFEE	DEFB $3C,$00	Where the repeat goes back to; while an object is updated, its height and z length (+10, +11)
WORK_KIND	FFF0	DEFB $00	While an object is updated, its kind byte (+12)
WORK_DIRECTION	FFF1	DEFB $FE	Its direction (+13): 0 bounces, 1 rises, 2 -x, 3 +x, 4 up, 5 down, 6 +z, 7 -z; the sprite drawing's flags
WORK_BEHAVIOUR	FFF2	DEFB $10	Its behaviour byte (+14)
DRAW_WIDTH	FFF3	DEFB $10	A sprite's width in bytes, while it is drawn; while an object is updated, its timer (+15)
WORK_WEIGHT	FFF4	DEFB $10	Its +16: 16 more than its weight, 0 if still; the length of the draw list while sprites are drawn
WORK_ANIMATION	FFF5	DEFB $10	Its animation byte (+17); rows, while a sprite is drawn
WORK_HEADING	FFF6	DEFB $10,$00	Its heading (+18); SP while CLEAR_512_BELOW borrows it; the fill's pointer to the row below
FOUND_RECORD	FFF8	DEFB $00	The number of the record FIND_OBSTACLE found (the author's T+20); SP while CLEAR_ROOM_SCREEN borrows it; the fill's texture; a sprite row's bytes (DRAW_SPRITE)
DRAW_INDEX	FFF9	DEFB $42	The record REDRAW_OBJECT is looking at
CLEAR_END	FFFA	DEFB $42	Where CLEAR_ROOM_SCREEN's clearing stopped
STEP_AXES	FFFB	DEFB $42	A move's axes: bit 0 x, 1 y, 2 z; 5 landed, 6 a climb, 7 into a door; the fill's pointer to this row
ASKED_DIRECTION	FFFC	DEFB $42	The direction a move asked for, before collisions changed it
WORK_RECORD	FFFD	DEFB $42	The record being updated; the fill's pointer to the row above
DRAW_COUNT	FFFE	DEFB $3C	Counts down the draw list; the high byte of WORK_RECORD
RIDE_DIRECTION	FFFF	DEFB $00	The direction of what the mover has landed on; the last entry in the draw list at BUFFER_DA00 ($FF: none)