Game 1Unit 1 of 101 hr learning time
The Dark Seeks the Light
The hunt generalises: a Manhattan scan over every lit lamp — and your own flame — replaces the single-target chase, and the wisp learns to take back what you lit, using your own saved-under trick against you.
10% of The Long Night
Open the file you finished Gloaming with — the real one, the build that matched the shipped game byte for byte. That’s this unit’s step 0, unchanged. Now win it twice and pay attention to the second run: the moment a lamp is lit, it’s solved. The wisp only ever wants you, so every lamp you light is a cell of the board that stops mattering. By the eighth, the night has nothing left to say. The playtest sheet for this game put it more bluntly: the draught is a hazard, not an antagonist — it menaces the lamplighter and never once touches the thing the game is actually about.
This module fixes that, and the fix starts with one question: what does the dark actually want? Not you. The light.
Milestone 1 — the nearest light
The wisp’s whole mind, as Gloaming shipped, was “seek the lamplighter”: copy his position into seek_col/seek_row and let the greater-axis chase do the rest. The upgrade keeps the chase untouched and generalises the seeking: every lit lamp is now a candidate prey, and so is your flame — you are just one more light in the square. The wisp wants whichever is nearest.
Nearest by what measure? Not a ruler’s distance — the number of steps: |dc| + |dr|, the distance a 4-connected walker actually pays. It’s called the Manhattan distance, after a city you can only cross by its grid, and it costs eleven instructions:
Step 1: manhattan, and the scan that keeps the nearest light
+62-4
| 669 | 669 | defb %11111111 | |
| 670 | 670 | | |
| 671 | 671 | ; ---------------------------------------------------------------------------- | |
| 672 | - | ; draught_step — the hunt. One rule: step one cell along the axis with | |
| 673 | - | ; the greater distance to the lamplighter (ties go sideways). No walls, | |
| 674 | - | ; no vetoes — the wisp is not of the town, and stone means nothing to it. | |
| 672 | + | ; manhattan — distance from the draught to cell (C = col, B = row) -> A. | |
| 673 | + | ; Grid distance, not straight-line: |dc| + |dr|, the number of steps a | |
| 674 | + | ; 4-connected walker needs — the only distance the night knows. | |
| 675 | + | ; ---------------------------------------------------------------------------- | |
| 676 | + | manhattan: | |
| 677 | + | ld a, (draught_col) | |
| 678 | + | sub c | |
| 679 | + | jp p, .dc | |
| 680 | + | neg | |
| 681 | + | .dc: | |
| 682 | + | ld d, a | |
| 683 | + | ld a, (draught_row) | |
| 684 | + | sub b | |
| 685 | + | jp p, .dr | |
| 686 | + | neg | |
| 687 | + | .dr: | |
| 688 | + | add a, d | |
| 689 | + | ret | |
| 690 | + | | |
| 691 | + | ; ---------------------------------------------------------------------------- | |
| 692 | + | ; draught_step — the hunt, generalised. The wisp steps toward the | |
| 693 | + | ; NEAREST LIGHT: a lit lamp, or the lamplighter's own flame. Same | |
| 694 | + | ; chase, new prey — and still no walls, no vetoes on the way. | |
| 675 | 695 | ; ---------------------------------------------------------------------------- | |
| 676 | 696 | draught_step: | |
| 677 | 697 | ld a, (draught_timer) | |
| ... | |||
| 681 | 701 | ld a, DRAUGHT_SPEED | |
| 682 | 702 | ld (draught_timer), a | |
| 683 | 703 | | |
| 684 | - | ; the dark hunts the lamplighter's own flame | |
| 704 | + | ; the lamplighter's flame is the first candidate... | |
| 685 | 705 | ld a, (lamp_col) | |
| 706 | + | ld c, a | |
| 686 | 707 | ld (seek_col), a | |
| 687 | 708 | ld a, (lamp_row) | |
| 709 | + | ld b, a | |
| 710 | + | ld (seek_row), a | |
| 711 | + | call manhattan | |
| 712 | + | ld (seek_best), a | |
| 713 | + | | |
| 714 | + | ; ...then every lit lamp, keeping the nearest. The lamp table | |
| 715 | + | ; names the candidates; the SCREEN says which are lit — the | |
| 716 | + | ; same attribute truth the collision system reads. | |
| 717 | + | ld hl, lamp_data | |
| 718 | + | .scan: | |
| 719 | + | ld a, (hl) | |
| 720 | + | cp $FF | |
| 721 | + | jr z, .chase | |
| 722 | + | ld c, a | |
| 723 | + | inc hl | |
| 724 | + | ld b, (hl) | |
| 725 | + | inc hl | |
| 726 | + | push hl | |
| 727 | + | push bc | |
| 728 | + | call attr_addr_cr | |
| 729 | + | ld a, (hl) | |
| 730 | + | pop bc | |
| 731 | + | cp LAMP_LIT | |
| 732 | + | jr nz, .dnext ; unlit lamps cast no light | |
| 733 | + | call manhattan | |
| 734 | + | ld hl, seek_best | |
| 735 | + | cp (hl) | |
| 736 | + | jr nc, .dnext ; not nearer — keep the current prey | |
| 737 | + | ld (hl), a | |
| 738 | + | ld a, c | |
| 739 | + | ld (seek_col), a | |
| 740 | + | ld a, b | |
| 688 | 741 | ld (seek_row), a | |
| 742 | + | .dnext: | |
| 743 | + | pop hl | |
| 744 | + | jr .scan | |
| 689 | 745 | | |
| 690 | 746 | .chase: | |
| 691 | 747 | ; step one cell along the axis with the greater distance | |
| ... | |||
| 1227 | 1283 | defb 0 | |
| 1228 | 1284 | seek_row: | |
| 1229 | 1285 | defb 0 | |
| 1286 | + | seek_best: | |
| 1287 | + | defb 0 ; the nearest distance found so far | |
| 1230 | 1288 | dtcol: | |
| 1231 | 1289 | defb 0 | |
| 1232 | 1290 | dtrow: |
The complete step 1 program
; The Long Night — Unit 1: The Dark Seeks the Light
; Cumulative build; every step runs on its own. Narrative: the unit page.
; Targeting generalises: nearest light — and your flame counts.
org 32768
COBBLE equ %00000001 ; PAPER black (0), INK blue (1) — dark ground
WALL equ %00001111 ; PAPER blue (1), INK white (7) — pale stone
WALL_BIT equ 3 ; the attribute bit that says "this is wall"
LAMP_ATTR equ %01000111 ; BRIGHT, PAPER black, INK white — his own light
LAMP_UNLIT equ %00000101 ; cold cyan INK on black PAPER — bit 3
; clear, so a lamp reads as floor
LAMP_LIT equ %01000110 ; BRIGHT yellow INK on black — a held flame
DRAUGHT_ATTR equ %01000101 ; the wisp: BRIGHT cyan on black — cold light
LIVES equ 3
LIFE_PIP equ %01010000 ; a life: BRIGHT red PAPER — a small ember
LIFE_BASE equ $5800 + 28 ; row 0, right of the ledge — three cells
DRAUGHT_SPEED equ 16 ; frames between the wisp's steps
DRAUGHT_COL0 equ 28 ; the corner the dark enters from
DRAUGHT_ROW0 equ 4
PIP_UNLIT equ %00101000 ; a cold pip: cyan PAPER, a solid block
PIP_LIT equ %01110000 ; a warm pip: BRIGHT yellow PAPER
PIP_BASE equ $5800 + 12 ; row 0, column 12 — the HUD ledge,
; eight cells, centred over the square
NUM_LAMPS equ 8
MSG_ATTR equ %01000111 ; message text: bright white on black
MSG_ROW equ 11
LOSE_COL equ 10 ; centres the eleven characters
WIN_COL equ 7 ; centres the seventeen characters
FONT equ $3C00 ; the ROM font, addressed so that
; ASCII x 8 lands on the right glyph
STATE_TITLE equ 0
STATE_PLAY equ 1
STATE_WIN equ 2 ; the night is held — the game is won
STATE_LOSE equ 3 ; night falls — the game is lost
LOCK equ 25 ; input-lock frames after entering a screen
SPEAKER equ %00010000 ; port $FE bit 4 — the beeper's one bit
TITLE_COL equ 12 ; GLOAMING, centred
PROMPT_COL equ 10 ; PRESS SPACE, centred
TITLE_ROW equ 8
PROMPT_ROW equ 14
CONT_ROW equ 16 ; "PRESS SPACE" under a win/lose line
START_COL equ 15 ; where the lamplighter begins
START_ROW equ 11
PLAYER_REPEAT equ 6 ; frames between steps while a key is held
GATHER equ 120 ; frames the dark gathers before its first step
KEYS_OP equ $DFFE ; half-row P O I U Y — bits 1 and 0
KEYS_Q equ $FBFE ; half-row Q W E R T — bit 0 is Q
KEYS_A equ $FDFE ; half-row A S D F G — bit 0 is A
KEYS_SPACE equ $7FFE ; half-row SPACE SYM M N B — bit 0
start:
; --- the border goes black — the night beyond the square ---
; Port $FE bits 0-2 set the BORDER colour. A = 0 = black.
ld a, 0
out ($FE), a
ld a, STATE_TITLE
ld (game_state), a
call draw_title_screen
im 1
ei
call chime_dusk ; after EI — the rests need the interrupt
main_loop:
halt
; the dispatch: each state names what a frame means — the
; title listens for a beginning, PLAY beats the game forward,
; WIN and LOSE hold the screen exactly as it stands
ld a, (game_state)
cp STATE_TITLE
jr z, .do_title
cp STATE_PLAY
jr z, .do_play
call end_step ; WIN or LOSE — wait for a key, then title
jr main_loop
.do_title:
call title_step
jr main_loop
.do_play:
call play_step
jr main_loop
; ----------------------------------------------------------------------------
; title_step — SPACE starts a fresh game.
; ----------------------------------------------------------------------------
title_step:
ld a, (input_lock)
or a
jr z, .tready
dec a
ld (input_lock), a
ret
.tready:
ld bc, KEYS_SPACE
in a, (c)
bit 0, a
ret nz
call init_game
ld a, STATE_PLAY
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; end_step — WIN or LOSE: SPACE returns to the title.
; ----------------------------------------------------------------------------
end_step:
ld a, (input_lock)
or a
jr z, .eready
dec a
ld (input_lock), a
ret
.eready:
ld bc, KEYS_SPACE
in a, (c)
bit 0, a
ret nz
call draw_title_screen
call chime_dusk
ld a, LOCK
ld (input_lock), a
ld a, STATE_TITLE
ld (game_state), a
ret
; play_step — one beat of the game: ask the keyboard.
play_step:
call player_step
; contact can end the game mid-frame — if it did, stop here
ld a, (game_state)
cp STATE_PLAY
ret nz
call draught_step
ld a, (game_state)
cp STATE_PLAY
ret nz
; the win check, at the only beat the count can have changed
ld a, (lit_count)
cp NUM_LAMPS
ret nz
; the night is held — the lives you kept are the score
ld a, (lives)
ld hl, best_lives
cp (hl)
jr c, .nobest
ld (hl), a
.nobest:
call draw_win_screen
call fanfare_held
ld a, LOCK
ld (input_lock), a
ld a, STATE_WIN
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; init_game — everything a fresh night needs, gathered from what was
; the boot sequence. Beginning is a callable thing now.
; ----------------------------------------------------------------------------
init_game:
xor a
ld (lit_count), a
ld a, LIVES
ld (lives), a
; --- place the lamplighter ---
; His position is data. Everything that draws him reads it.
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
; --- and, in the far corner, something else ---
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
; the dark gathers before its first step — a beat to read
; the square before the hunt begins
ld a, GATHER
ld (draught_timer), a
xor a
ld (player_timer), a
; --- wipe the canvas ---
; The bitmap ($4000-$57FF) is the pixel layer; whatever was on
; screen before us still lives there. Zero it so only our
; attribute colours show.
call clear_bitmap
; --- texture the ground ---
; Blit the cobble stipple into every cell's bitmap, rows 1-23.
; The attributes will colour these pixels in a moment.
call fill_ground
; --- wash in the cobbles ---
; Seed the first attribute cell, point DE one cell ahead, and
; let LDIR cascade the byte through all 768 cells.
ld hl, $5800
ld de, $5801
ld (hl), COBBLE
ld bc, 767
ldir
call warm_walls
call paint_buildings
; --- brick the walls ---
; Now that the wall cells are painted, fill_walls can read the
; map back and lay brick wherever the wall bit is set.
call fill_walls
call draw_pips
call draw_lives
call draw_lamps
; save what he is about to stand on, BEFORE the first draw
call save_under
call draw_lamp
call save_draught
call draw_draught
ret
; ----------------------------------------------------------------------------
; warm_walls — the square's edge, one attribute write per cell; the
; colour is no longer a constant but the wall_ramp entry for how many
; lamps are lit. Same painting loop as ever — only where C comes from
; has changed.
; ----------------------------------------------------------------------------
warm_walls:
ld a, (lit_count)
ld e, a
ld d, 0
ld hl, wall_ramp
add hl, de
ld c, (hl) ; the byte every wall cell gets
; the top wall: row 1 is 32 cells in a row from $5820
; (row 0 is kept back — it becomes the HUD later)
ld hl, $5820
ld b, 32
.wt:
ld (hl), c
inc hl
djnz .wt
; the bottom wall: row 23, 32 cells from $5AE0
ld hl, $5AE0
ld b, 32
.wb:
ld (hl), c
inc hl
djnz .wb
; the side walls: column 0 and column 31 of rows 1-23.
; Write the row's first cell, hop 31 cells to its last,
; then step a full row (32) down — 23 times.
ld hl, $5820
ld b, 23
.ws:
ld (hl), c
push hl
ld de, 31
add hl, de
ld (hl), c
pop hl
ld de, 32
add hl, de
djnz .ws
ret
; ----------------------------------------------------------------------------
; The beeper. One bit on port $FE: set it, wait, clear it, wait — a
; square wave by hand. C is the half-period (pitch: bigger is lower),
; B the number of cycles (duration). DI while it sounds: the 50 Hz
; interrupt would stretch random half-periods and buzz the tone.
; ----------------------------------------------------------------------------
beep:
di
.bcyc:
ld a, SPEAKER
out ($FE), a
ld a, c
.bd1:
dec a
jr nz, .bd1
xor a
out ($FE), a
ld a, c
.bd2:
dec a
jr nz, .bd2
djnz .bcyc
ei
ret
blip_lit: ; a rising third — the lamp catches
ld b, $17 ; C6
ld c, $67
call beep
ld b, $28 ; E6
ld c, $51
jp beep
chime_dusk: ; two cold tolls, then the motif far off
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 10
call rest
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 13
call rest
ld b, $92 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $9D ; C5
ld c, $CF
jp beep
; rest — B frames of silence. Musical time rides the heartbeat: the
; gaps between notes are counted in HALTs, not busy-loops.
rest:
halt
djnz rest
ret
fanfare_held: ; THE NIGHT IS HELD — a rising run
ld b, $83 ; C5
ld c, $CF
call beep
ld b, 3
call rest
ld b, $A5 ; E5
ld c, $A4
call beep
ld b, 3
call rest
ld b, $C4 ; G5
ld c, $8A
call beep
ld b, 3
call rest
ld b, $FF ; C6, held — B only counts to 255,
ld c, $67
call beep
ld b, $FF ; so hold it by sounding it twice
ld c, $67
jp beep
sting_nightfall: ; NIGHT FALLS — two steps down, then dark
ld b, $53 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $49 ; D5
ld c, $B8
call beep
ld b, 4
call rest
ld b, $DC ; A4, long — the night settles on it
ld c, $F7
jp beep
; ----------------------------------------------------------------------------
; Screens.
; ----------------------------------------------------------------------------
; draw_win_screen — lift the lamplighter off the board (restore his
; cell: the eighth lamp, lit, comes out of the buffer), then say it.
; draw_title_screen — sparse and suggestive: a black void, the name,
; the invitation. Everything else is left to the imagination, which
; is both the aesthetic and the budget.
draw_title_screen:
call clear_bitmap
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, title_text
ld b, TITLE_ROW
ld c, TITLE_COL
call print_string
ld hl, prompt_text
ld b, PROMPT_ROW
ld c, PROMPT_COL
call print_string
; your best night — the lives you kept on your finest win,
; read in lamps (no digits). It survives the loop back to
; the title: the go-again hook.
ld hl, $5800 + 11 * 32 + 14
ld b, LIVES
ld a, (best_lives)
ld c, a
.tpip:
ld a, PIP_UNLIT
inc c
dec c
jr z, .tpcold
ld a, PIP_LIT
dec c
.tpcold:
ld (hl), a
inc hl
djnz .tpip
ret
draw_win_screen:
call restore_under
ld hl, win_text
ld b, MSG_ROW
ld c, WIN_COL
call print_string
ld hl, prompt_text
ld b, CONT_ROW
ld c, PROMPT_COL
call print_string
ret
; draw_lose_screen — the whole attribute table goes black: every lamp,
; every wall, every warm cell, gone in one LDIR. Then the words.
draw_lose_screen:
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, lose_text
ld b, MSG_ROW
ld c, LOSE_COL
call print_string
ld hl, prompt_text
ld b, CONT_ROW
ld c, PROMPT_COL
call print_string
ret
; ----------------------------------------------------------------------------
; clear_bitmap — zero the pixel layer, $4000-$57FF, with the same
; seed-and-cascade LDIR idiom the cobble wash uses.
; ----------------------------------------------------------------------------
clear_bitmap:
ld hl, $4000
ld de, $4001
ld (hl), 0
ld bc, 6143
ldir
ret
; ----------------------------------------------------------------------------
; player_step — the keys become movement. Each direction key edits a
; TARGET position (tcol, trow) — a proposal, not yet a move — so it
; can be vetoed before it becomes real. Then the move commits: leave
; the old cell, take the new one, draw.
; ----------------------------------------------------------------------------
player_step:
; --- propose: the target starts where he stands ---
ld a, (lamp_col)
ld (tcol), a
ld a, (lamp_row)
ld (trow), a
; The held-key gate: the first press steps at once, then one
; step every PLAYER_REPEAT frames. Releasing every direction
; key re-arms the instant first step, so taps stay crisp.
ld bc, KEYS_OP
in a, (c)
cpl
and %00000011
ld e, a
ld bc, KEYS_Q
in a, (c)
cpl
and %00000001
or e
ld e, a
ld bc, KEYS_A
in a, (c)
cpl
and %00000001
or e
jr nz, .held
xor a
ld (player_timer), a
ret
.held:
ld a, (player_timer)
or a
jr z, .stepnow
dec a
ld (player_timer), a
ret
.stepnow:
ld a, PLAYER_REPEAT
ld (player_timer), a
ld bc, KEYS_OP
in a, (c)
bit 1, a ; O — a zero bit is a pressed key
jr z, .pleft
bit 0, a ; P, same half-row
jr z, .pright
ld bc, KEYS_Q
in a, (c)
bit 0, a ; Q
jr z, .pup
ld bc, KEYS_A
in a, (c)
bit 0, a ; A
jr z, .pdown
ret ; nothing held — nothing to do
.pleft:
ld hl, tcol
dec (hl)
jr .pmove
.pright:
ld hl, tcol
inc (hl)
jr .pmove
.pup:
ld hl, trow
dec (hl)
jr .pmove
.pdown:
ld hl, trow
inc (hl)
.pmove:
; The veto: ask the target cell's attribute whether it's wall.
; NZ means brick — the proposal dies here and he stays put.
ld a, (trow)
ld b, a
ld a, (tcol)
ld c, a
call wall_at
ret nz
; and the mirror rule: he cannot step onto the wisp either
ld a, (tcol)
ld hl, draught_col
cp (hl)
jr nz, .pcommit
ld a, (trow)
ld hl, draught_row
cp (hl)
jr nz, .pcommit
call lose_life ; walking into the cold costs the same
ret
.pcommit:
; --- commit: restore, step, save, draw — in that order ---
call restore_under
ld a, (tcol)
ld (lamp_col), a
ld a, (trow)
ld (lamp_row), a
call save_under
; light it where it lives: while he covers the lamp, its truth
; is the buffer — rewrite the saved attribute, and restore will
; paint the lamp back lit when he leaves
ld a, (under_lamp + 8)
cp LAMP_UNLIT
jr nz, .pdrawn
ld a, LAMP_LIT
ld (under_lamp + 8), a
call light_pip
call blip_lit
call warm_walls
.pdrawn:
call draw_lamp
ret
; ----------------------------------------------------------------------------
; fill_ground — the cobble stipple. Not decoration: the stipple is what
; makes ground-state changes visible later, when the game starts
; recolouring these pixels. Rows 1-23 (row 0 is the HUD).
; ----------------------------------------------------------------------------
fill_ground:
ld b, 1 ; rows 1-23 (row 0 is the HUD)
.fgr:
ld c, 0
.fgc:
ld de, cobble_tex
call blit_tex
inc c
ld a, c
cp 32
jr c, .fgc
inc b
ld a, b
cp 24
jr c, .fgr
ret
; fill_walls — brickwork. Driven by the wall attribute bit, so anything
; painted as wall — now or later in the game — gets its brick for free:
; the map itself decides where the brick goes.
fill_walls:
ld b, 1
.fwr:
ld c, 0
.fwc:
push bc
call attr_addr_cr
bit WALL_BIT, (hl)
pop bc
jr z, .fwn
ld de, brick_tex
call blit_tex
.fwn:
inc c
ld a, c
cp 32
jr c, .fwc
inc b
ld a, b
cp 24
jr c, .fwr
ret
; blit_tex — write the 8-byte texture at DE into cell (C, B)'s bitmap.
; scr_addr_cr finds the cell's first pixel row; INC H steps down the
; other seven, 256 bytes apart.
blit_tex:
push bc
call scr_addr_cr
ld b, 8
.bt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .bt
pop bc
ret
cobble_tex:
defb %10000010
defb %00000000
defb %00001000
defb %00000000
defb %00100001
defb %00000000
defb %00010000
defb %00000000
brick_tex:
; mortar courses with staggered verticals — dusk-lit stone
defb %00001000
defb %00001000
defb %00001000
defb %11111111
defb %10000000
defb %10000000
defb %10000000
defb %11111111
; ----------------------------------------------------------------------------
; manhattan — distance from the draught to cell (C = col, B = row) -> A.
; Grid distance, not straight-line: |dc| + |dr|, the number of steps a
; 4-connected walker needs — the only distance the night knows.
; ----------------------------------------------------------------------------
manhattan:
ld a, (draught_col)
sub c
jp p, .dc
neg
.dc:
ld d, a
ld a, (draught_row)
sub b
jp p, .dr
neg
.dr:
add a, d
ret
; ----------------------------------------------------------------------------
; draught_step — the hunt, generalised. The wisp steps toward the
; NEAREST LIGHT: a lit lamp, or the lamplighter's own flame. Same
; chase, new prey — and still no walls, no vetoes on the way.
; ----------------------------------------------------------------------------
draught_step:
ld a, (draught_timer)
dec a
ld (draught_timer), a
ret nz
ld a, DRAUGHT_SPEED
ld (draught_timer), a
; the lamplighter's flame is the first candidate...
ld a, (lamp_col)
ld c, a
ld (seek_col), a
ld a, (lamp_row)
ld b, a
ld (seek_row), a
call manhattan
ld (seek_best), a
; ...then every lit lamp, keeping the nearest. The lamp table
; names the candidates; the SCREEN says which are lit — the
; same attribute truth the collision system reads.
ld hl, lamp_data
.scan:
ld a, (hl)
cp $FF
jr z, .chase
ld c, a
inc hl
ld b, (hl)
inc hl
push hl
push bc
call attr_addr_cr
ld a, (hl)
pop bc
cp LAMP_LIT
jr nz, .dnext ; unlit lamps cast no light
call manhattan
ld hl, seek_best
cp (hl)
jr nc, .dnext ; not nearer — keep the current prey
ld (hl), a
ld a, c
ld (seek_col), a
ld a, b
ld (seek_row), a
.dnext:
pop hl
jr .scan
.chase:
; step one cell along the axis with the greater distance
; (ties go sideways) — the night is 4-connected, like the
; lamplighter
ld a, (draught_col)
ld (dtcol), a
ld a, (draught_row)
ld (dtrow), a
ld a, (seek_col)
ld hl, draught_col
sub (hl)
jp p, .absc
neg
.absc:
ld d, a ; D = |dc|
ld a, (seek_row)
ld hl, draught_row
sub (hl)
jp p, .absr
neg
.absr:
cp d ; |dr| vs |dc|
jr z, .tie
jr c, .horiz
jr .vert
.tie:
ld a, d
or a
ret z ; already on the light
jr .horiz
.horiz:
ld a, (seek_col)
ld hl, draught_col
cp (hl)
jr c, .hleft
ld a, (hl)
inc a
ld (dtcol), a
jr .contact
.hleft:
ld a, (hl)
dec a
ld (dtcol), a
jr .contact
.vert:
ld a, (seek_row)
ld hl, draught_row
cp (hl)
jr c, .vup
ld a, (hl)
inc a
ld (dtrow), a
jr .contact
.vup:
ld a, (hl)
dec a
ld (dtrow), a
.contact:
; never step ONTO the lamplighter: adjacent is as close as
; the night comes. Two movers, two buffers — and one cell
; can only ever be under one of them.
ld a, (dtcol)
ld hl, lamp_col
cp (hl)
jr nz, .dmove
ld a, (dtrow)
ld hl, lamp_row
cp (hl)
jr nz, .dmove
call lose_life ; the touch, priced
ret
.dmove:
call restore_draught
ld a, (dtcol)
ld (draught_col), a
ld a, (dtrow)
ld (draught_row), a
call save_draught
call draw_draught
ret
; paint_buildings — walk the rectangle table: each entry is col, row,
; width, height; $FF ends the list. Every cell inside a rectangle gets
; the WALL attribute — and because fill_walls textures by the wall bit,
; the brickwork arrives without another line of drawing code.
paint_buildings:
ld hl, bldg_data
.pb:
ld a, (hl)
cp $FF
ret z
ld c, a ; col
inc hl
ld b, (hl) ; row
inc hl
ld d, (hl) ; width
inc hl
ld e, (hl) ; height
inc hl
push hl
.pbrow:
push bc
push de
.pbcol:
push bc
push de
call attr_addr_cr
ld (hl), WALL
pop de
pop bc
inc c
dec d
jr nz, .pbcol
pop de
pop bc
inc b
dec e
jr nz, .pbrow
pop hl
jr .pb
bldg_data:
defb 5, 5, 4, 3
defb 23, 5, 4, 3
defb $FF
; ----------------------------------------------------------------------------
; lose_life — the price of the touch: one ember out, and either a
; fresh start or the fall of night.
; ----------------------------------------------------------------------------
lose_life:
ld a, (lives)
dec a
ld (lives), a
ld e, a
ld d, 0
ld hl, LIFE_BASE
add hl, de
ld (hl), COBBLE ; the ember at the new count goes out
ld a, (lives)
or a
jr z, .gone
; a life left: the lamplighter returns to the start cell
call restore_under
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
call save_under
call draw_lamp
; the taking costs the night its reach — the wisp recoils to
; the far corner, so every life buys a whole fresh chase
; (leaving it beside the respawn made a catch strip every
; life in seconds once the draught learnt to hunt)
call restore_draught
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
ld a, DRAUGHT_SPEED
ld (draught_timer), a
call save_draught
call draw_draught
ret
.gone:
call draw_lose_screen
call sting_nightfall
ld a, LOCK
ld (input_lock), a
ld a, STATE_LOSE
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; print_string / print_char — the machine's own letters. The Spectrum
; keeps its font in ROM: eight bytes per character, and FONT is chosen
; so that ASCII code x 8 + FONT is the glyph's address. Each character
; is drawn like any cell: attribute first, eight rows down the cell.
; ----------------------------------------------------------------------------
print_string:
.ps:
ld a, (hl)
cp $FF
ret z
push hl
push bc
call print_char
pop bc
pop hl
inc hl
inc c
jr .ps
print_char:
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
ld de, FONT
add hl, de
ex de, hl
push de
call attr_addr_cr
ld (hl), MSG_ATTR
call scr_addr_cr
pop de
ld b, 8
.pc:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .pc
ret
; ----------------------------------------------------------------------------
; light_pip / draw_pips / draw_lives.
; ----------------------------------------------------------------------------
; light_pip — warm the next pip along and count the lamp. lit_count is
; the index of the pip to light AND the number of lamps lit so far —
; read it for the address, then step it.
light_pip:
ld a, (lit_count)
ld e, a
ld d, 0
inc a
ld (lit_count), a
ld hl, PIP_BASE
add hl, de
ld (hl), PIP_LIT
ret
; draw_pips — the tally row: one cell per lamp on the HUD ledge, all
; cold to start. A pip is pure attribute — no glyph, just a block of
; PAPER — so the row costs eight bytes of screen and no bitmap at all.
draw_pips:
ld hl, PIP_BASE
ld b, NUM_LAMPS
ld a, PIP_UNLIT
.dp:
ld (hl), a
inc hl
djnz .dp
ret
; draw_lives — three embers on the ledge's right shoulder.
draw_lives:
ld hl, LIFE_BASE
ld b, LIVES
ld a, LIFE_PIP
.dlv:
ld (hl), a
inc hl
djnz .dlv
ret
; ----------------------------------------------------------------------------
; draw_lamps — walk the position table: col, row pairs, $FF to finish.
; Placement is data; the drawing code neither knows nor cares how many
; lamps the town has tonight.
; ----------------------------------------------------------------------------
draw_lamps:
ld hl, lamp_data
.next:
ld a, (hl)
cp $FF
ret z
ld c, a
inc hl
ld b, (hl)
inc hl
push hl
call draw_lantern
pop hl
jr .next
; draw_lantern — an unlit lamp into cell (C, B): cold cyan attribute,
; then the lantern glyph down the cell like any texture.
draw_lantern:
call attr_addr_cr
ld (hl), LAMP_UNLIT
call scr_addr_cr
ld de, lantern
ld b, 8
.dlt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dlt
ret
; ----------------------------------------------------------------------------
; scr_addr_cr — HL = bitmap address of cell (C, B)'s first pixel row.
; The row's top two bits pick the third of the screen (H), its bottom
; three become L's top bits, and the column fills L's low five.
; ----------------------------------------------------------------------------
scr_addr_cr:
ld a, b
and %00011000 ; the third (row bits 4-3) ...
or %01000000 ; ... under the screen base $40xx
ld h, a
ld a, b
and %00000111 ; the char row within the third ...
rrca ; ... rotated into bits 7-5
rrca
rrca
or c ; the column in bits 4-0
ld l, a
ret
; attr_addr_cr — HL = attribute address of cell (C, B):
; $5800 + row*32 + col, the row shifted up five times.
attr_addr_cr:
ld a, b
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld de, $5800
add hl, de
ld a, c
ld e, a
ld d, 0
add hl, de
ret
; wall_at — is cell (C, B) wall? The answer is already on the screen:
; every wall cell's attribute has WALL_BIT set, so one bit-test of
; attribute memory is the whole collision system. NZ = wall.
wall_at:
call attr_addr_cr
bit WALL_BIT, (hl)
ret
; ----------------------------------------------------------------------------
; The lamplighter's save / restore / draw.
; ----------------------------------------------------------------------------
; pos_bc — the lamplighter's cell into (C, B), read fresh from the data.
pos_bc:
ld a, (lamp_row)
ld b, a
ld a, (lamp_col)
ld c, a
ret
; save_under — copy the nine bytes of his cell into the buffer: eight
; bitmap rows, then the attribute. Runs as he ARRIVES, before the
; draw — so the buffer always holds true ground, never him.
save_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.su:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .su
call pos_bc
call attr_addr_cr
ld a, (hl)
ld (under_lamp + 8), a
ret
; restore_under — the same nine bytes back the other way: the ground
; returns exactly as it was. Runs as he LEAVES, while the position
; still points at the old cell.
restore_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.ru:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .ru
call pos_bc
call attr_addr_cr
ld a, (under_lamp + 8)
ld (hl), a
ret
draw_lamp:
; his colour first: the cell's attribute becomes his own —
; bright white on the black, his own light about him
call pos_bc
call attr_addr_cr
ld (hl), LAMP_ATTR
; then his shape, eight bytes down the cell like any texture
call pos_bc
call scr_addr_cr
ld de, lamplighter
ld b, 8
.dl:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dl
ret
; ----------------------------------------------------------------------------
; The draught's save / restore / draw — the lamplighter's engine, twice.
; Same loops, same nine-byte contract, its own buffer and its own
; position: two movers can share a world but never a buffer.
; ----------------------------------------------------------------------------
dpos_bc:
ld a, (draught_row)
ld b, a
ld a, (draught_col)
ld c, a
ret
save_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.sd:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .sd
call dpos_bc
call attr_addr_cr
ld a, (hl)
ld (under_draught + 8), a
ret
restore_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.rd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .rd
call dpos_bc
call attr_addr_cr
ld a, (under_draught + 8)
ld (hl), a
ret
draw_draught:
call dpos_bc
call attr_addr_cr
ld (hl), DRAUGHT_ATTR
call dpos_bc
call scr_addr_cr
ld de, draught_glyph
ld b, 8
.dd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dd
ret
; ----------------------------------------------------------------------------
; Data.
; ----------------------------------------------------------------------------
game_state:
defb STATE_TITLE
input_lock:
defb 0
wall_ramp:
; The square warms in the game's own vocabulary: the stone
; stays dusk-blue; the lamplight catches the mortar first
; (ink white -> yellow), then the whole face glows BRIGHT.
; Never magenta — warmth is yellow here, not red-shifted blue.
defb %00001111 ; dusk stone, white mortar
defb %00001111
defb %00001111
defb %00001110 ; the mortar warms — yellow ink
defb %00001110
defb %00001110
defb %01001110 ; the stone catches the glow — BRIGHT
defb %01001110
defb %01110000 ; all eight lit: the square aglow —
; warm yellow stone, only at the win
lamp_data:
defb 4, 3
defb 27, 3
defb 9, 7
defb 22, 7
defb 6, 15
defb 25, 15
defb 13, 20
defb 18, 20
defb $FF
lamp_col:
defb START_COL
lamp_row:
defb START_ROW
tcol:
defb 0
trow:
defb 0
lit_count:
defb 0
lives:
defb LIVES
best_lives:
defb 0 ; lives kept on the finest win — never reset
draught_col:
defb 28
draught_row:
defb 4
draught_timer:
defb 16
player_timer:
defb 0
seek_col:
defb 0
seek_row:
defb 0
seek_best:
defb 0 ; the nearest distance found so far
dtcol:
defb 0
dtrow:
defb 0
under_lamp:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
under_draught:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
lamplighter:
defb %00111100
defb %00111100
defb %00011000
defb %01111110
defb %00011000
defb %00011000
defb %00100100
defb %01000010
lantern:
defb %00011000
defb %00100100
defb %01111110
defb %01111110
defb %01011010
defb %01111110
defb %01111110
defb %00111100
draught_glyph:
defb %00000000
defb %00111100
defb %01111110
defb %11111111
defb %11111111
defb %01111110
defb %00111100
defb %00000000
title_text:
defb "GLOAMING"
defb $FF
prompt_text:
defb "PRESS SPACE"
defb $FF
win_text:
defb "THE NIGHT IS HELD"
defb $FF
lose_text:
defb "NIGHT FALLS"
defb $FF
end start
Read the scan’s shape: the flame goes in first as the candidate to beat, then every lamp in lamp_data gets a turn — and only the lit ones compete. How does the wisp know which are lit? The same way the collision system knows which cells are wall: it asks the screen. attr_addr_cr on the lamp’s cell, compare with LAMP_LIT, done. The attribute map has been this game’s single source of truth since Gloaming unit 9, and the new AI reads it like everything else does. Note the tie-break too: jr nc, .dnext keeps the current prey unless a lamp is strictly nearer — so with nothing lit, or everything equal, it still comes for you.
Watch what it does when it arrives, though:
Milestone 2 — the snuff
Here is the unit’s best idea, and it’s one you already own. In Gloaming unit 12 you lit lamps with a single byte: while the lamplighter stands on a lamp, the lamp’s truth lives in his under-buffer, so rewriting under_lamp + 8 from cold to lit made his own departure paint the lamp alight. Stepping onto state changes it — the saved byte is the rule.
The wisp has an under-buffer too. Run the same trick in the other direction:
Step 2: the snuff — the buffer-edit trick, performed by the villain
+27-1
| 823 | 823 | ld a, (dtrow) | |
| 824 | 824 | ld (draught_row), a | |
| 825 | 825 | call save_draught | |
| 826 | + | ; the snuff: while the wisp covers a lit lamp, the lamp's | |
| 827 | + | ; truth is ITS buffer — the same saved-under rule that lights | |
| 828 | + | ; lamps beneath the lamplighter, run by the villain. Rewrite | |
| 829 | + | ; the saved attribute to cold, and the wisp's own restore | |
| 830 | + | ; will leave the lamp out as it moves on. | |
| 831 | + | ld a, (under_draught + 8) | |
| 832 | + | cp LAMP_LIT | |
| 833 | + | jr nz, .nosnuff | |
| 834 | + | ld a, LAMP_UNLIT | |
| 835 | + | ld (under_draught + 8), a | |
| 836 | + | call unlight_pip | |
| 837 | + | call warm_walls | |
| 838 | + | .nosnuff: | |
| 826 | 839 | call draw_draught | |
| 827 | 840 | ret | |
| 828 | 841 | | |
| ... | |||
| 962 | 975 | ret | |
| 963 | 976 | | |
| 964 | 977 | ; ---------------------------------------------------------------------------- | |
| 965 | - | ; light_pip / draw_pips / draw_lives. | |
| 978 | + | ; light_pip / unlight_pip / draw_pips / draw_lives. | |
| 966 | 979 | ; ---------------------------------------------------------------------------- | |
| 967 | 980 | | |
| 968 | 981 | ; light_pip — warm the next pip along and count the lamp. lit_count is | |
| ... | |||
| 977 | 990 | ld hl, PIP_BASE | |
| 978 | 991 | add hl, de | |
| 979 | 992 | ld (hl), PIP_LIT | |
| 993 | + | ret | |
| 994 | + | | |
| 995 | + | ; unlight_pip — light_pip's mirror: step the count back and cool the | |
| 996 | + | ; pip at the new count. The tally can go DOWN now. | |
| 997 | + | unlight_pip: | |
| 998 | + | ld a, (lit_count) | |
| 999 | + | dec a | |
| 1000 | + | ld (lit_count), a | |
| 1001 | + | ld e, a | |
| 1002 | + | ld d, 0 | |
| 1003 | + | ld hl, PIP_BASE | |
| 1004 | + | add hl, de | |
| 1005 | + | ld (hl), PIP_UNLIT | |
| 980 | 1006 | ret | |
| 981 | 1007 | | |
| 982 | 1008 | ; draw_pips — the tally row: one cell per lamp on the HUD ledge, all |
The complete step 2 program
; The Long Night — Unit 1: The Dark Seeks the Light
; Cumulative build; every step runs on its own. Narrative: the unit page.
; Targeting generalises: nearest light — and your flame counts.
org 32768
COBBLE equ %00000001 ; PAPER black (0), INK blue (1) — dark ground
WALL equ %00001111 ; PAPER blue (1), INK white (7) — pale stone
WALL_BIT equ 3 ; the attribute bit that says "this is wall"
LAMP_ATTR equ %01000111 ; BRIGHT, PAPER black, INK white — his own light
LAMP_UNLIT equ %00000101 ; cold cyan INK on black PAPER — bit 3
; clear, so a lamp reads as floor
LAMP_LIT equ %01000110 ; BRIGHT yellow INK on black — a held flame
DRAUGHT_ATTR equ %01000101 ; the wisp: BRIGHT cyan on black — cold light
LIVES equ 3
LIFE_PIP equ %01010000 ; a life: BRIGHT red PAPER — a small ember
LIFE_BASE equ $5800 + 28 ; row 0, right of the ledge — three cells
DRAUGHT_SPEED equ 16 ; frames between the wisp's steps
DRAUGHT_COL0 equ 28 ; the corner the dark enters from
DRAUGHT_ROW0 equ 4
PIP_UNLIT equ %00101000 ; a cold pip: cyan PAPER, a solid block
PIP_LIT equ %01110000 ; a warm pip: BRIGHT yellow PAPER
PIP_BASE equ $5800 + 12 ; row 0, column 12 — the HUD ledge,
; eight cells, centred over the square
NUM_LAMPS equ 8
MSG_ATTR equ %01000111 ; message text: bright white on black
MSG_ROW equ 11
LOSE_COL equ 10 ; centres the eleven characters
WIN_COL equ 7 ; centres the seventeen characters
FONT equ $3C00 ; the ROM font, addressed so that
; ASCII x 8 lands on the right glyph
STATE_TITLE equ 0
STATE_PLAY equ 1
STATE_WIN equ 2 ; the night is held — the game is won
STATE_LOSE equ 3 ; night falls — the game is lost
LOCK equ 25 ; input-lock frames after entering a screen
SPEAKER equ %00010000 ; port $FE bit 4 — the beeper's one bit
TITLE_COL equ 12 ; GLOAMING, centred
PROMPT_COL equ 10 ; PRESS SPACE, centred
TITLE_ROW equ 8
PROMPT_ROW equ 14
CONT_ROW equ 16 ; "PRESS SPACE" under a win/lose line
START_COL equ 15 ; where the lamplighter begins
START_ROW equ 11
PLAYER_REPEAT equ 6 ; frames between steps while a key is held
GATHER equ 120 ; frames the dark gathers before its first step
KEYS_OP equ $DFFE ; half-row P O I U Y — bits 1 and 0
KEYS_Q equ $FBFE ; half-row Q W E R T — bit 0 is Q
KEYS_A equ $FDFE ; half-row A S D F G — bit 0 is A
KEYS_SPACE equ $7FFE ; half-row SPACE SYM M N B — bit 0
start:
; --- the border goes black — the night beyond the square ---
; Port $FE bits 0-2 set the BORDER colour. A = 0 = black.
ld a, 0
out ($FE), a
ld a, STATE_TITLE
ld (game_state), a
call draw_title_screen
im 1
ei
call chime_dusk ; after EI — the rests need the interrupt
main_loop:
halt
; the dispatch: each state names what a frame means — the
; title listens for a beginning, PLAY beats the game forward,
; WIN and LOSE hold the screen exactly as it stands
ld a, (game_state)
cp STATE_TITLE
jr z, .do_title
cp STATE_PLAY
jr z, .do_play
call end_step ; WIN or LOSE — wait for a key, then title
jr main_loop
.do_title:
call title_step
jr main_loop
.do_play:
call play_step
jr main_loop
; ----------------------------------------------------------------------------
; title_step — SPACE starts a fresh game.
; ----------------------------------------------------------------------------
title_step:
ld a, (input_lock)
or a
jr z, .tready
dec a
ld (input_lock), a
ret
.tready:
ld bc, KEYS_SPACE
in a, (c)
bit 0, a
ret nz
call init_game
ld a, STATE_PLAY
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; end_step — WIN or LOSE: SPACE returns to the title.
; ----------------------------------------------------------------------------
end_step:
ld a, (input_lock)
or a
jr z, .eready
dec a
ld (input_lock), a
ret
.eready:
ld bc, KEYS_SPACE
in a, (c)
bit 0, a
ret nz
call draw_title_screen
call chime_dusk
ld a, LOCK
ld (input_lock), a
ld a, STATE_TITLE
ld (game_state), a
ret
; play_step — one beat of the game: ask the keyboard.
play_step:
call player_step
; contact can end the game mid-frame — if it did, stop here
ld a, (game_state)
cp STATE_PLAY
ret nz
call draught_step
ld a, (game_state)
cp STATE_PLAY
ret nz
; the win check, at the only beat the count can have changed
ld a, (lit_count)
cp NUM_LAMPS
ret nz
; the night is held — the lives you kept are the score
ld a, (lives)
ld hl, best_lives
cp (hl)
jr c, .nobest
ld (hl), a
.nobest:
call draw_win_screen
call fanfare_held
ld a, LOCK
ld (input_lock), a
ld a, STATE_WIN
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; init_game — everything a fresh night needs, gathered from what was
; the boot sequence. Beginning is a callable thing now.
; ----------------------------------------------------------------------------
init_game:
xor a
ld (lit_count), a
ld a, LIVES
ld (lives), a
; --- place the lamplighter ---
; His position is data. Everything that draws him reads it.
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
; --- and, in the far corner, something else ---
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
; the dark gathers before its first step — a beat to read
; the square before the hunt begins
ld a, GATHER
ld (draught_timer), a
xor a
ld (player_timer), a
; --- wipe the canvas ---
; The bitmap ($4000-$57FF) is the pixel layer; whatever was on
; screen before us still lives there. Zero it so only our
; attribute colours show.
call clear_bitmap
; --- texture the ground ---
; Blit the cobble stipple into every cell's bitmap, rows 1-23.
; The attributes will colour these pixels in a moment.
call fill_ground
; --- wash in the cobbles ---
; Seed the first attribute cell, point DE one cell ahead, and
; let LDIR cascade the byte through all 768 cells.
ld hl, $5800
ld de, $5801
ld (hl), COBBLE
ld bc, 767
ldir
call warm_walls
call paint_buildings
; --- brick the walls ---
; Now that the wall cells are painted, fill_walls can read the
; map back and lay brick wherever the wall bit is set.
call fill_walls
call draw_pips
call draw_lives
call draw_lamps
; save what he is about to stand on, BEFORE the first draw
call save_under
call draw_lamp
call save_draught
call draw_draught
ret
; ----------------------------------------------------------------------------
; warm_walls — the square's edge, one attribute write per cell; the
; colour is no longer a constant but the wall_ramp entry for how many
; lamps are lit. Same painting loop as ever — only where C comes from
; has changed.
; ----------------------------------------------------------------------------
warm_walls:
ld a, (lit_count)
ld e, a
ld d, 0
ld hl, wall_ramp
add hl, de
ld c, (hl) ; the byte every wall cell gets
; the top wall: row 1 is 32 cells in a row from $5820
; (row 0 is kept back — it becomes the HUD later)
ld hl, $5820
ld b, 32
.wt:
ld (hl), c
inc hl
djnz .wt
; the bottom wall: row 23, 32 cells from $5AE0
ld hl, $5AE0
ld b, 32
.wb:
ld (hl), c
inc hl
djnz .wb
; the side walls: column 0 and column 31 of rows 1-23.
; Write the row's first cell, hop 31 cells to its last,
; then step a full row (32) down — 23 times.
ld hl, $5820
ld b, 23
.ws:
ld (hl), c
push hl
ld de, 31
add hl, de
ld (hl), c
pop hl
ld de, 32
add hl, de
djnz .ws
ret
; ----------------------------------------------------------------------------
; The beeper. One bit on port $FE: set it, wait, clear it, wait — a
; square wave by hand. C is the half-period (pitch: bigger is lower),
; B the number of cycles (duration). DI while it sounds: the 50 Hz
; interrupt would stretch random half-periods and buzz the tone.
; ----------------------------------------------------------------------------
beep:
di
.bcyc:
ld a, SPEAKER
out ($FE), a
ld a, c
.bd1:
dec a
jr nz, .bd1
xor a
out ($FE), a
ld a, c
.bd2:
dec a
jr nz, .bd2
djnz .bcyc
ei
ret
blip_lit: ; a rising third — the lamp catches
ld b, $17 ; C6
ld c, $67
call beep
ld b, $28 ; E6
ld c, $51
jp beep
chime_dusk: ; two cold tolls, then the motif far off
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 10
call rest
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 13
call rest
ld b, $92 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $9D ; C5
ld c, $CF
jp beep
; rest — B frames of silence. Musical time rides the heartbeat: the
; gaps between notes are counted in HALTs, not busy-loops.
rest:
halt
djnz rest
ret
fanfare_held: ; THE NIGHT IS HELD — a rising run
ld b, $83 ; C5
ld c, $CF
call beep
ld b, 3
call rest
ld b, $A5 ; E5
ld c, $A4
call beep
ld b, 3
call rest
ld b, $C4 ; G5
ld c, $8A
call beep
ld b, 3
call rest
ld b, $FF ; C6, held — B only counts to 255,
ld c, $67
call beep
ld b, $FF ; so hold it by sounding it twice
ld c, $67
jp beep
sting_nightfall: ; NIGHT FALLS — two steps down, then dark
ld b, $53 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $49 ; D5
ld c, $B8
call beep
ld b, 4
call rest
ld b, $DC ; A4, long — the night settles on it
ld c, $F7
jp beep
; ----------------------------------------------------------------------------
; Screens.
; ----------------------------------------------------------------------------
; draw_win_screen — lift the lamplighter off the board (restore his
; cell: the eighth lamp, lit, comes out of the buffer), then say it.
; draw_title_screen — sparse and suggestive: a black void, the name,
; the invitation. Everything else is left to the imagination, which
; is both the aesthetic and the budget.
draw_title_screen:
call clear_bitmap
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, title_text
ld b, TITLE_ROW
ld c, TITLE_COL
call print_string
ld hl, prompt_text
ld b, PROMPT_ROW
ld c, PROMPT_COL
call print_string
; your best night — the lives you kept on your finest win,
; read in lamps (no digits). It survives the loop back to
; the title: the go-again hook.
ld hl, $5800 + 11 * 32 + 14
ld b, LIVES
ld a, (best_lives)
ld c, a
.tpip:
ld a, PIP_UNLIT
inc c
dec c
jr z, .tpcold
ld a, PIP_LIT
dec c
.tpcold:
ld (hl), a
inc hl
djnz .tpip
ret
draw_win_screen:
call restore_under
ld hl, win_text
ld b, MSG_ROW
ld c, WIN_COL
call print_string
ld hl, prompt_text
ld b, CONT_ROW
ld c, PROMPT_COL
call print_string
ret
; draw_lose_screen — the whole attribute table goes black: every lamp,
; every wall, every warm cell, gone in one LDIR. Then the words.
draw_lose_screen:
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, lose_text
ld b, MSG_ROW
ld c, LOSE_COL
call print_string
ld hl, prompt_text
ld b, CONT_ROW
ld c, PROMPT_COL
call print_string
ret
; ----------------------------------------------------------------------------
; clear_bitmap — zero the pixel layer, $4000-$57FF, with the same
; seed-and-cascade LDIR idiom the cobble wash uses.
; ----------------------------------------------------------------------------
clear_bitmap:
ld hl, $4000
ld de, $4001
ld (hl), 0
ld bc, 6143
ldir
ret
; ----------------------------------------------------------------------------
; player_step — the keys become movement. Each direction key edits a
; TARGET position (tcol, trow) — a proposal, not yet a move — so it
; can be vetoed before it becomes real. Then the move commits: leave
; the old cell, take the new one, draw.
; ----------------------------------------------------------------------------
player_step:
; --- propose: the target starts where he stands ---
ld a, (lamp_col)
ld (tcol), a
ld a, (lamp_row)
ld (trow), a
; The held-key gate: the first press steps at once, then one
; step every PLAYER_REPEAT frames. Releasing every direction
; key re-arms the instant first step, so taps stay crisp.
ld bc, KEYS_OP
in a, (c)
cpl
and %00000011
ld e, a
ld bc, KEYS_Q
in a, (c)
cpl
and %00000001
or e
ld e, a
ld bc, KEYS_A
in a, (c)
cpl
and %00000001
or e
jr nz, .held
xor a
ld (player_timer), a
ret
.held:
ld a, (player_timer)
or a
jr z, .stepnow
dec a
ld (player_timer), a
ret
.stepnow:
ld a, PLAYER_REPEAT
ld (player_timer), a
ld bc, KEYS_OP
in a, (c)
bit 1, a ; O — a zero bit is a pressed key
jr z, .pleft
bit 0, a ; P, same half-row
jr z, .pright
ld bc, KEYS_Q
in a, (c)
bit 0, a ; Q
jr z, .pup
ld bc, KEYS_A
in a, (c)
bit 0, a ; A
jr z, .pdown
ret ; nothing held — nothing to do
.pleft:
ld hl, tcol
dec (hl)
jr .pmove
.pright:
ld hl, tcol
inc (hl)
jr .pmove
.pup:
ld hl, trow
dec (hl)
jr .pmove
.pdown:
ld hl, trow
inc (hl)
.pmove:
; The veto: ask the target cell's attribute whether it's wall.
; NZ means brick — the proposal dies here and he stays put.
ld a, (trow)
ld b, a
ld a, (tcol)
ld c, a
call wall_at
ret nz
; and the mirror rule: he cannot step onto the wisp either
ld a, (tcol)
ld hl, draught_col
cp (hl)
jr nz, .pcommit
ld a, (trow)
ld hl, draught_row
cp (hl)
jr nz, .pcommit
call lose_life ; walking into the cold costs the same
ret
.pcommit:
; --- commit: restore, step, save, draw — in that order ---
call restore_under
ld a, (tcol)
ld (lamp_col), a
ld a, (trow)
ld (lamp_row), a
call save_under
; light it where it lives: while he covers the lamp, its truth
; is the buffer — rewrite the saved attribute, and restore will
; paint the lamp back lit when he leaves
ld a, (under_lamp + 8)
cp LAMP_UNLIT
jr nz, .pdrawn
ld a, LAMP_LIT
ld (under_lamp + 8), a
call light_pip
call blip_lit
call warm_walls
.pdrawn:
call draw_lamp
ret
; ----------------------------------------------------------------------------
; fill_ground — the cobble stipple. Not decoration: the stipple is what
; makes ground-state changes visible later, when the game starts
; recolouring these pixels. Rows 1-23 (row 0 is the HUD).
; ----------------------------------------------------------------------------
fill_ground:
ld b, 1 ; rows 1-23 (row 0 is the HUD)
.fgr:
ld c, 0
.fgc:
ld de, cobble_tex
call blit_tex
inc c
ld a, c
cp 32
jr c, .fgc
inc b
ld a, b
cp 24
jr c, .fgr
ret
; fill_walls — brickwork. Driven by the wall attribute bit, so anything
; painted as wall — now or later in the game — gets its brick for free:
; the map itself decides where the brick goes.
fill_walls:
ld b, 1
.fwr:
ld c, 0
.fwc:
push bc
call attr_addr_cr
bit WALL_BIT, (hl)
pop bc
jr z, .fwn
ld de, brick_tex
call blit_tex
.fwn:
inc c
ld a, c
cp 32
jr c, .fwc
inc b
ld a, b
cp 24
jr c, .fwr
ret
; blit_tex — write the 8-byte texture at DE into cell (C, B)'s bitmap.
; scr_addr_cr finds the cell's first pixel row; INC H steps down the
; other seven, 256 bytes apart.
blit_tex:
push bc
call scr_addr_cr
ld b, 8
.bt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .bt
pop bc
ret
cobble_tex:
defb %10000010
defb %00000000
defb %00001000
defb %00000000
defb %00100001
defb %00000000
defb %00010000
defb %00000000
brick_tex:
; mortar courses with staggered verticals — dusk-lit stone
defb %00001000
defb %00001000
defb %00001000
defb %11111111
defb %10000000
defb %10000000
defb %10000000
defb %11111111
; ----------------------------------------------------------------------------
; manhattan — distance from the draught to cell (C = col, B = row) -> A.
; Grid distance, not straight-line: |dc| + |dr|, the number of steps a
; 4-connected walker needs — the only distance the night knows.
; ----------------------------------------------------------------------------
manhattan:
ld a, (draught_col)
sub c
jp p, .dc
neg
.dc:
ld d, a
ld a, (draught_row)
sub b
jp p, .dr
neg
.dr:
add a, d
ret
; ----------------------------------------------------------------------------
; draught_step — the hunt, generalised. The wisp steps toward the
; NEAREST LIGHT: a lit lamp, or the lamplighter's own flame. Same
; chase, new prey — and still no walls, no vetoes on the way.
; ----------------------------------------------------------------------------
draught_step:
ld a, (draught_timer)
dec a
ld (draught_timer), a
ret nz
ld a, DRAUGHT_SPEED
ld (draught_timer), a
; the lamplighter's flame is the first candidate...
ld a, (lamp_col)
ld c, a
ld (seek_col), a
ld a, (lamp_row)
ld b, a
ld (seek_row), a
call manhattan
ld (seek_best), a
; ...then every lit lamp, keeping the nearest. The lamp table
; names the candidates; the SCREEN says which are lit — the
; same attribute truth the collision system reads.
ld hl, lamp_data
.scan:
ld a, (hl)
cp $FF
jr z, .chase
ld c, a
inc hl
ld b, (hl)
inc hl
push hl
push bc
call attr_addr_cr
ld a, (hl)
pop bc
cp LAMP_LIT
jr nz, .dnext ; unlit lamps cast no light
call manhattan
ld hl, seek_best
cp (hl)
jr nc, .dnext ; not nearer — keep the current prey
ld (hl), a
ld a, c
ld (seek_col), a
ld a, b
ld (seek_row), a
.dnext:
pop hl
jr .scan
.chase:
; step one cell along the axis with the greater distance
; (ties go sideways) — the night is 4-connected, like the
; lamplighter
ld a, (draught_col)
ld (dtcol), a
ld a, (draught_row)
ld (dtrow), a
ld a, (seek_col)
ld hl, draught_col
sub (hl)
jp p, .absc
neg
.absc:
ld d, a ; D = |dc|
ld a, (seek_row)
ld hl, draught_row
sub (hl)
jp p, .absr
neg
.absr:
cp d ; |dr| vs |dc|
jr z, .tie
jr c, .horiz
jr .vert
.tie:
ld a, d
or a
ret z ; already on the light
jr .horiz
.horiz:
ld a, (seek_col)
ld hl, draught_col
cp (hl)
jr c, .hleft
ld a, (hl)
inc a
ld (dtcol), a
jr .contact
.hleft:
ld a, (hl)
dec a
ld (dtcol), a
jr .contact
.vert:
ld a, (seek_row)
ld hl, draught_row
cp (hl)
jr c, .vup
ld a, (hl)
inc a
ld (dtrow), a
jr .contact
.vup:
ld a, (hl)
dec a
ld (dtrow), a
.contact:
; never step ONTO the lamplighter: adjacent is as close as
; the night comes. Two movers, two buffers — and one cell
; can only ever be under one of them.
ld a, (dtcol)
ld hl, lamp_col
cp (hl)
jr nz, .dmove
ld a, (dtrow)
ld hl, lamp_row
cp (hl)
jr nz, .dmove
call lose_life ; the touch, priced
ret
.dmove:
call restore_draught
ld a, (dtcol)
ld (draught_col), a
ld a, (dtrow)
ld (draught_row), a
call save_draught
; the snuff: while the wisp covers a lit lamp, the lamp's
; truth is ITS buffer — the same saved-under rule that lights
; lamps beneath the lamplighter, run by the villain. Rewrite
; the saved attribute to cold, and the wisp's own restore
; will leave the lamp out as it moves on.
ld a, (under_draught + 8)
cp LAMP_LIT
jr nz, .nosnuff
ld a, LAMP_UNLIT
ld (under_draught + 8), a
call unlight_pip
call warm_walls
.nosnuff:
call draw_draught
ret
; paint_buildings — walk the rectangle table: each entry is col, row,
; width, height; $FF ends the list. Every cell inside a rectangle gets
; the WALL attribute — and because fill_walls textures by the wall bit,
; the brickwork arrives without another line of drawing code.
paint_buildings:
ld hl, bldg_data
.pb:
ld a, (hl)
cp $FF
ret z
ld c, a ; col
inc hl
ld b, (hl) ; row
inc hl
ld d, (hl) ; width
inc hl
ld e, (hl) ; height
inc hl
push hl
.pbrow:
push bc
push de
.pbcol:
push bc
push de
call attr_addr_cr
ld (hl), WALL
pop de
pop bc
inc c
dec d
jr nz, .pbcol
pop de
pop bc
inc b
dec e
jr nz, .pbrow
pop hl
jr .pb
bldg_data:
defb 5, 5, 4, 3
defb 23, 5, 4, 3
defb $FF
; ----------------------------------------------------------------------------
; lose_life — the price of the touch: one ember out, and either a
; fresh start or the fall of night.
; ----------------------------------------------------------------------------
lose_life:
ld a, (lives)
dec a
ld (lives), a
ld e, a
ld d, 0
ld hl, LIFE_BASE
add hl, de
ld (hl), COBBLE ; the ember at the new count goes out
ld a, (lives)
or a
jr z, .gone
; a life left: the lamplighter returns to the start cell
call restore_under
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
call save_under
call draw_lamp
; the taking costs the night its reach — the wisp recoils to
; the far corner, so every life buys a whole fresh chase
; (leaving it beside the respawn made a catch strip every
; life in seconds once the draught learnt to hunt)
call restore_draught
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
ld a, DRAUGHT_SPEED
ld (draught_timer), a
call save_draught
call draw_draught
ret
.gone:
call draw_lose_screen
call sting_nightfall
ld a, LOCK
ld (input_lock), a
ld a, STATE_LOSE
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; print_string / print_char — the machine's own letters. The Spectrum
; keeps its font in ROM: eight bytes per character, and FONT is chosen
; so that ASCII code x 8 + FONT is the glyph's address. Each character
; is drawn like any cell: attribute first, eight rows down the cell.
; ----------------------------------------------------------------------------
print_string:
.ps:
ld a, (hl)
cp $FF
ret z
push hl
push bc
call print_char
pop bc
pop hl
inc hl
inc c
jr .ps
print_char:
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
ld de, FONT
add hl, de
ex de, hl
push de
call attr_addr_cr
ld (hl), MSG_ATTR
call scr_addr_cr
pop de
ld b, 8
.pc:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .pc
ret
; ----------------------------------------------------------------------------
; light_pip / unlight_pip / draw_pips / draw_lives.
; ----------------------------------------------------------------------------
; light_pip — warm the next pip along and count the lamp. lit_count is
; the index of the pip to light AND the number of lamps lit so far —
; read it for the address, then step it.
light_pip:
ld a, (lit_count)
ld e, a
ld d, 0
inc a
ld (lit_count), a
ld hl, PIP_BASE
add hl, de
ld (hl), PIP_LIT
ret
; unlight_pip — light_pip's mirror: step the count back and cool the
; pip at the new count. The tally can go DOWN now.
unlight_pip:
ld a, (lit_count)
dec a
ld (lit_count), a
ld e, a
ld d, 0
ld hl, PIP_BASE
add hl, de
ld (hl), PIP_UNLIT
ret
; draw_pips — the tally row: one cell per lamp on the HUD ledge, all
; cold to start. A pip is pure attribute — no glyph, just a block of
; PAPER — so the row costs eight bytes of screen and no bitmap at all.
draw_pips:
ld hl, PIP_BASE
ld b, NUM_LAMPS
ld a, PIP_UNLIT
.dp:
ld (hl), a
inc hl
djnz .dp
ret
; draw_lives — three embers on the ledge's right shoulder.
draw_lives:
ld hl, LIFE_BASE
ld b, LIVES
ld a, LIFE_PIP
.dlv:
ld (hl), a
inc hl
djnz .dlv
ret
; ----------------------------------------------------------------------------
; draw_lamps — walk the position table: col, row pairs, $FF to finish.
; Placement is data; the drawing code neither knows nor cares how many
; lamps the town has tonight.
; ----------------------------------------------------------------------------
draw_lamps:
ld hl, lamp_data
.next:
ld a, (hl)
cp $FF
ret z
ld c, a
inc hl
ld b, (hl)
inc hl
push hl
call draw_lantern
pop hl
jr .next
; draw_lantern — an unlit lamp into cell (C, B): cold cyan attribute,
; then the lantern glyph down the cell like any texture.
draw_lantern:
call attr_addr_cr
ld (hl), LAMP_UNLIT
call scr_addr_cr
ld de, lantern
ld b, 8
.dlt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dlt
ret
; ----------------------------------------------------------------------------
; scr_addr_cr — HL = bitmap address of cell (C, B)'s first pixel row.
; The row's top two bits pick the third of the screen (H), its bottom
; three become L's top bits, and the column fills L's low five.
; ----------------------------------------------------------------------------
scr_addr_cr:
ld a, b
and %00011000 ; the third (row bits 4-3) ...
or %01000000 ; ... under the screen base $40xx
ld h, a
ld a, b
and %00000111 ; the char row within the third ...
rrca ; ... rotated into bits 7-5
rrca
rrca
or c ; the column in bits 4-0
ld l, a
ret
; attr_addr_cr — HL = attribute address of cell (C, B):
; $5800 + row*32 + col, the row shifted up five times.
attr_addr_cr:
ld a, b
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld de, $5800
add hl, de
ld a, c
ld e, a
ld d, 0
add hl, de
ret
; wall_at — is cell (C, B) wall? The answer is already on the screen:
; every wall cell's attribute has WALL_BIT set, so one bit-test of
; attribute memory is the whole collision system. NZ = wall.
wall_at:
call attr_addr_cr
bit WALL_BIT, (hl)
ret
; ----------------------------------------------------------------------------
; The lamplighter's save / restore / draw.
; ----------------------------------------------------------------------------
; pos_bc — the lamplighter's cell into (C, B), read fresh from the data.
pos_bc:
ld a, (lamp_row)
ld b, a
ld a, (lamp_col)
ld c, a
ret
; save_under — copy the nine bytes of his cell into the buffer: eight
; bitmap rows, then the attribute. Runs as he ARRIVES, before the
; draw — so the buffer always holds true ground, never him.
save_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.su:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .su
call pos_bc
call attr_addr_cr
ld a, (hl)
ld (under_lamp + 8), a
ret
; restore_under — the same nine bytes back the other way: the ground
; returns exactly as it was. Runs as he LEAVES, while the position
; still points at the old cell.
restore_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.ru:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .ru
call pos_bc
call attr_addr_cr
ld a, (under_lamp + 8)
ld (hl), a
ret
draw_lamp:
; his colour first: the cell's attribute becomes his own —
; bright white on the black, his own light about him
call pos_bc
call attr_addr_cr
ld (hl), LAMP_ATTR
; then his shape, eight bytes down the cell like any texture
call pos_bc
call scr_addr_cr
ld de, lamplighter
ld b, 8
.dl:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dl
ret
; ----------------------------------------------------------------------------
; The draught's save / restore / draw — the lamplighter's engine, twice.
; Same loops, same nine-byte contract, its own buffer and its own
; position: two movers can share a world but never a buffer.
; ----------------------------------------------------------------------------
dpos_bc:
ld a, (draught_row)
ld b, a
ld a, (draught_col)
ld c, a
ret
save_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.sd:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .sd
call dpos_bc
call attr_addr_cr
ld a, (hl)
ld (under_draught + 8), a
ret
restore_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.rd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .rd
call dpos_bc
call attr_addr_cr
ld a, (under_draught + 8)
ld (hl), a
ret
draw_draught:
call dpos_bc
call attr_addr_cr
ld (hl), DRAUGHT_ATTR
call dpos_bc
call scr_addr_cr
ld de, draught_glyph
ld b, 8
.dd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dd
ret
; ----------------------------------------------------------------------------
; Data.
; ----------------------------------------------------------------------------
game_state:
defb STATE_TITLE
input_lock:
defb 0
wall_ramp:
; The square warms in the game's own vocabulary: the stone
; stays dusk-blue; the lamplight catches the mortar first
; (ink white -> yellow), then the whole face glows BRIGHT.
; Never magenta — warmth is yellow here, not red-shifted blue.
defb %00001111 ; dusk stone, white mortar
defb %00001111
defb %00001111
defb %00001110 ; the mortar warms — yellow ink
defb %00001110
defb %00001110
defb %01001110 ; the stone catches the glow — BRIGHT
defb %01001110
defb %01110000 ; all eight lit: the square aglow —
; warm yellow stone, only at the win
lamp_data:
defb 4, 3
defb 27, 3
defb 9, 7
defb 22, 7
defb 6, 15
defb 25, 15
defb 13, 20
defb 18, 20
defb $FF
lamp_col:
defb START_COL
lamp_row:
defb START_ROW
tcol:
defb 0
trow:
defb 0
lit_count:
defb 0
lives:
defb LIVES
best_lives:
defb 0 ; lives kept on the finest win — never reset
draught_col:
defb 28
draught_row:
defb 4
draught_timer:
defb 16
player_timer:
defb 0
seek_col:
defb 0
seek_row:
defb 0
seek_best:
defb 0 ; the nearest distance found so far
dtcol:
defb 0
dtrow:
defb 0
under_lamp:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
under_draught:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
lamplighter:
defb %00111100
defb %00111100
defb %00011000
defb %01111110
defb %00011000
defb %00011000
defb %00100100
defb %01000010
lantern:
defb %00011000
defb %00100100
defb %01111110
defb %01111110
defb %01011010
defb %01111110
defb %01111110
defb %00111100
draught_glyph:
defb %00000000
defb %00111100
defb %01111110
defb %11111111
defb %11111111
defb %01111110
defb %00111100
defb %00000000
title_text:
defb "GLOAMING"
defb $FF
prompt_text:
defb "PRESS SPACE"
defb $FF
win_text:
defb "THE NIGHT IS HELD"
defb $FF
lose_text:
defb "NIGHT FALLS"
defb $FF
end start
unlight_pip is light_pip reflected — the count steps back, the pip at the new count goes cold — and warm_walls re-reads the ramp so the square’s glow honestly retreats with the count. The night can now undo you, and every piece of machinery it used was already on the board: the buffer, the tally, the ramp. Villainy turned out to be four lines.
One more thing to notice: the taking is silent. A lamp that dies with no sound at all is genuinely unsettling — but the real reason is discipline, the same one Gloaming kept: sound is a finish-phase concern, and this module’s finish phase will give the snuff its voice alongside the bells it belongs with. Feel the silence for now; you’ll appreciate the falling third more when it arrives.
When it’s wrong, see why
- The wisp ignores lit lamps entirely. The scan is comparing the wrong thing — it must read the lamp cell’s attribute and compare with
LAMP_LIT, not test the lamp table itself. The table says where lamps are; only the screen says which are alight. - It hunts a lamp that isn’t lit. Same line, inverted: your branch on the compare is backwards, or you’re testing
LAMP_UNLIT. - It never chases you at all. The flame must be loaded as the first candidate before the scan, with its distance in
seek_best— miss that and an empty queue of lit lamps leaves the seek pointing at stale data. - The pip count drifts. Every snuff must run the pair: rewrite the buffered attribute and call
unlight_pip. One without the other and the tally lies — this game’s displays only stay honest because every change goes through its counter. - It sits beside the lamp and never takes it. Your snuff checks the wrong buffer byte. The lamp’s truth while covered is
under_draught + 8— the attribute slot, the ninth byte, not the bitmap rows before it.
Before and after
Gloaming’s draught wanted one thing and the board was furniture. Now the board is the contest: everything you claim becomes something it wants, your own flame is just one candidate among them, and the mechanism it robs you with is the very one you used to build progress in the first place. The design lesson sits in that symmetry — the strongest villains don’t get new machinery, they get your machinery with opposite intent. The behavioural lesson comes next, because if you played step 2 for more than a minute you already know what’s wrong with it.
Try this: feel the relentlessness
Play a full dusk against step 2 and try to win. After each snuff the wisp re-targets instantly — nearest light, again, forever, with no pause and no shape. It’s effective. It is also, in the words of the playtest that redesigned this game, “a pain in the bum” — pressure without rhythm reads as harassment, not menace. Name what’s missing before the next unit tells you.
Try this: a night with no self-preservation
Delete the flame-as-first-candidate block, so the wisp only ever wants lamps. The game gets strictly easier — you can stand anywhere — and yet the opening gets strange: with nothing lit, the wisp has no target at all and simply waits. An enemy that ignores you until you make progress is a real design (several tower-defence games are built on it); decide what it does to this one, then put the flame back.
What you’ve learnt
- Manhattan distance —
|dc| + |dr|, the honest metric of a grid, in eleven instructions. - A candidate scan: seed with a default, challenge with each contender, keep the winner — the shape of every “find the best X” loop you’ll ever write.
- The screen as shared truth: the AI reads the same attribute map the collision and paint systems use; nobody keeps a private list of what’s lit.
- Mechanics mirror: the saved-under rewrite that lights lamps also snuffs them;
unlight_pipislight_pipbackwards. Villains are cheapest when they reuse the hero’s verbs. - Reaching and taking are separate mechanics — and a game can be wrong in the gap between them.
What’s next
The wisp takes your lamps and never stops coming — efficient, shapeless, exhausting. Unit 2 gives its behaviour a rhythm: after every theft it carries the prize home and rests, and the game gets its breath back. The lesson has a famous ancestor, and its name is on an arcade cabinet.