Game 1 Unit 11 of 64 1 hr learning time
Defensive AI
The AI now blocks your expansion too. Balances offense and defense for smarter play.
17% of Ink War
The Unit 10 AI expands its own territory but ignores the human completely. If you build a large connected region, it won’t try to stop you. This unit adds defensive awareness — the AI now considers blocking human expansion as valuable as growing its own territory.
The result is a significantly more competitive opponent. It’s no longer just racing to fill the board; it’s actively fighting for contested cells.
Run It
pasmonext --sna inkwar.asm inkwar.sna
Watch how the AI positions itself. It doesn’t just expand outward — it claims cells that would otherwise extend your territory.
The Strategic Shift
In Unit 10, the AI scored each cell by counting adjacent AI cells. A cell with 2 AI neighbours scored higher than one with 1. But adjacent human cells were ignored.
Now we count both:
- Offense: Adjacent AI cells (expanding territory)
- Defense: Adjacent human cells (blocking expansion)
The combined score determines which cell to claim. A cell adjacent to 2 human cells and 1 AI cell scores 3 — the same as a cell adjacent to 3 AI cells. This makes contested boundary cells high priority.
Combined Scoring
The updated algorithm counts both types of neighbours:
; ----------------------------------------------------------------------------
; Find Best Cell (Offense + Defense)
; ----------------------------------------------------------------------------
; Returns A = index of empty cell with best combined score, or $FF if none
; Score = adjacent AI cells (offense) + adjacent human cells (defense)
; This makes the AI both expand territory AND block the human
find_best_adjacent_cell:
; Initialize best tracking
ld a, $ff
ld (best_cell), a ; No best cell yet
xor a
ld (best_score), a ; Best score = 0
; Scan all 64 cells
ld c, 0 ; C = current cell index
.fbac_loop:
; Check if cell is empty
ld hl, board_state
ld d, 0
ld e, c
add hl, de
ld a, (hl)
or a
jr nz, .fbac_next ; Not empty, skip
; Empty cell - count adjacent AI cells (offense)
push bc
ld a, c
call count_adjacent_ai
ld b, a ; B = AI adjacent count
; Count adjacent human cells (defense)
ld a, c
call count_adjacent_p1
add a, b ; A = combined score (AI + P1)
pop bc
; Compare with best score
ld b, a ; B = this score
ld a, (best_score)
cp b
jr nc, .fbac_next ; Current best >= this score
; New best found
ld a, b
ld (best_score), a
ld a, c
ld (best_cell), a
.fbac_next:
inc c
ld a, c
cp 64
jr c, .fbac_loop ; Continue if c < 64
; ... fallback to random if no adjacent cells
Two function calls now: count_adjacent_ai (from Unit 10) plus the new count_adjacent_p1. The scores are simply added together — no weighting, just raw neighbour count.
Counting Human Neighbours
The new function mirrors count_adjacent_ai, but checks for STATE_P1 instead of STATE_P2:
; ----------------------------------------------------------------------------
; Count Adjacent Human Cells
; ----------------------------------------------------------------------------
; A = cell index (0-63)
; Returns A = count of adjacent cells owned by human (P1)
count_adjacent_p1:
ld (temp_cell), a
xor a
ld (adj_count), a
; Get row and column
ld a, (temp_cell)
ld b, a
and %00000111 ; Column
ld c, a
ld a, b
rrca
rrca
rrca
and %00000111 ; Row
ld b, a ; B = row, C = col
; Check up (row-1)
ld a, b
or a
jr z, .cap_skip_up ; Row 0, no up neighbor
dec a ; Row - 1
push bc
ld b, a
call .cap_check_cell
pop bc
.cap_skip_up:
; Check down, left, right... (same pattern)
ld a, (adj_count)
ret
; Helper: check if cell at (B,C) is human owned
.cap_check_cell:
; Calculate index: row*8 + col
ld a, b
rlca
rlca
rlca ; Row * 8
add a, c ; + col
ld hl, board_state
ld d, 0
ld e, a
add hl, de
ld a, (hl)
cp STATE_P1 ; Human is Player 1
ret nz ; Not human cell
; Human cell - increment count
ld a, (adj_count)
inc a
ld (adj_count), a
ret
Same boundary checks, same helper pattern. The only difference is which player state we’re looking for.
Why Simple Addition Works
You might expect defense to need higher weighting — shouldn’t blocking be more important than expanding? In practice, simple addition works well:
- Early game: Few neighbours of either type, so random cells get picked
- Mid game: Contested boundaries naturally score highest (neighbours on both sides)
- Late game: Remaining cells tend to be near both players anyway
The AI doesn’t need explicit priorities because contested cells inherently have high combined scores.
The Behaviour Change
Compare the two AI versions:
Unit 10 (Offense Only):
- Claims cells adjacent to own territory
- Ignores human expansion entirely
- Lets you build large regions unopposed
Unit 11 (Offense + Defense):
- Values boundary cells between territories
- Actively contests your expansion
- Creates interleaved, competitive positions
The defensive AI is noticeably harder to beat. It won’t let you quietly dominate one side of the board.
The Complete Code
; ============================================================================
; INK WAR - Unit 11: Defensive AI
; ============================================================================
; AI now considers both offense and defense. Scores cells by:
; - Adjacent AI cells (expansion) + Adjacent human cells (blocking)
; Blocks human territory growth while still building its own.
;
; Controls: Q=Up, A=Down, O=Left, P=Right, SPACE=Claim
; 1=Two Player, 2=vs Computer (on title screen)
; ============================================================================
org 32768
; ----------------------------------------------------------------------------
; Constants
; ----------------------------------------------------------------------------
ATTR_BASE equ $5800
DISPLAY_FILE equ $4000
CHAR_SET equ $3C00 ; ROM character set base address
BOARD_ROW equ 8
BOARD_COL equ 12
BOARD_SIZE equ 8
; Display positions
SCORE_ROW equ 2 ; Score display row
P1_SCORE_COL equ 10 ; "P1: nn" column
P2_SCORE_COL equ 18 ; "P2: nn" column
TURN_ROW equ 4 ; Turn indicator row
TURN_COL equ 14 ; Turn indicator column
RESULT_ROW equ 20 ; Winner message row
RESULT_COL equ 11 ; Winner message column
; Game constants
TOTAL_CELLS equ 64 ; 8x8 board
; Customised colours (from Unit 3)
EMPTY_ATTR equ %01101000 ; Cyan paper + BRIGHT
BORDER_ATTR equ %01110000 ; Yellow paper + BRIGHT
CURSOR_ATTR equ %01111000 ; White paper + BRIGHT
P1_ATTR equ %01010000 ; Red paper + BRIGHT
P2_ATTR equ %01001000 ; Blue paper + BRIGHT
P1_CURSOR equ %01111010 ; White paper + Red ink + BRIGHT
P2_CURSOR equ %01111001 ; White paper + Blue ink + BRIGHT
; Text display attributes
TEXT_ATTR equ %00111000 ; White paper, black ink
P1_TEXT equ %01010111 ; Red paper, white ink + BRIGHT
P2_TEXT equ %01001111 ; Blue paper, white ink + BRIGHT
P1_BORDER equ 2
P2_BORDER equ 1
ERROR_BORDER equ 2 ; Red border for errors
; Keyboard ports
KEY_PORT equ $fe
ROW_QAOP equ $fb
ROW_ASDF equ $fd
ROW_YUIOP equ $df
ROW_SPACE equ $7f
; Cell states
STATE_EMPTY equ 0
STATE_P1 equ 1
STATE_P2 equ 2
; Game states (state machine)
GS_TITLE equ 0
GS_PLAYING equ 1
GS_RESULTS equ 2
; Game modes
GM_TWO_PLAYER equ 0
GM_VS_AI equ 1
; AI timing
AI_DELAY equ 25 ; Frames before AI moves (~0.5 sec)
; Title screen positions
TITLE_ROW equ 8
TITLE_COL equ 12 ; "INK WAR" (7 chars) centred: (32-7)/2=12.5
MODE1_ROW equ 14 ; "1 - TWO PLAYER"
MODE1_COL equ 9 ; (32-14)/2 = 9
MODE2_ROW equ 16 ; "2 - VS COMPUTER"
MODE2_COL equ 8 ; (32-15)/2 = 8.5
; Results screen positions
CONTINUE_ROW equ 22 ; "PRESS ANY KEY" after results
CONTINUE_COL equ 9 ; (32-13)/2 = 9.5
; Input timing
KEY_DELAY equ 8 ; Frames between key repeats
; ----------------------------------------------------------------------------
; Entry Point
; ----------------------------------------------------------------------------
start:
; Start at title screen
ld a, GS_TITLE
ld (game_state), a
call init_screen
call draw_title_screen
; Black border for title
xor a
out (KEY_PORT), a
main_loop:
halt
; Dispatch based on game state
ld a, (game_state)
or a
jr z, state_title ; GS_TITLE = 0
cp GS_PLAYING
jr z, state_playing
; Must be GS_RESULTS - handled inline after game over
jp main_loop
; ----------------------------------------------------------------------------
; State: Title
; ----------------------------------------------------------------------------
; Waits for 1 (Two Player) or 2 (vs Computer)
ROW_12345 equ $f7 ; Keyboard row for 1,2,3,4,5
state_title:
; Check for key 1 (Two Player)
ld a, ROW_12345
in a, (KEY_PORT)
bit 0, a ; Key 1
jr z, .st_two_player
; Check for key 2 (vs Computer)
bit 1, a ; Key 2
jr z, .st_vs_ai
jp main_loop ; No valid key - keep waiting
.st_two_player:
xor a ; GM_TWO_PLAYER = 0
ld (game_mode), a
call start_game
jp main_loop
.st_vs_ai:
ld a, GM_VS_AI
ld (game_mode), a
call start_game
jp main_loop
; ----------------------------------------------------------------------------
; State: Playing
; ----------------------------------------------------------------------------
state_playing:
; Check if AI's turn (Player 2 in vs AI mode)
ld a, (game_mode)
or a
jr z, .sp_human ; Two player mode - human controls
; vs AI mode - check if Player 2's turn
ld a, (current_player)
cp 2
jr z, .sp_ai_turn
.sp_human:
; Human player's turn
call read_keyboard
call handle_input
jp main_loop
.sp_ai_turn:
; AI's turn - use delay counter
ld a, (ai_timer)
or a
jr z, .sp_ai_move ; Timer expired, make move
; Still waiting
dec a
ld (ai_timer), a
jp main_loop
.sp_ai_move:
; Reset timer for next AI turn
ld a, AI_DELAY
ld (ai_timer), a
; AI makes a move
call ai_make_move
jp main_loop
; ----------------------------------------------------------------------------
; Start Game
; ----------------------------------------------------------------------------
; Transitions from title to playing state
start_game:
ld a, GS_PLAYING
ld (game_state), a
call init_screen
call init_game
call draw_board_border
call draw_board
call draw_ui
call draw_cursor
call update_border
; Wait for key release before playing
call wait_key_release
ret
; ----------------------------------------------------------------------------
; Initialise Screen
; ----------------------------------------------------------------------------
init_screen:
xor a
out (KEY_PORT), a
; Clear display file (pixels)
ld hl, DISPLAY_FILE
ld de, DISPLAY_FILE+1
ld bc, 6143
ld (hl), 0
ldir
; Clear all attributes to white paper, black ink
ld hl, ATTR_BASE
ld de, ATTR_BASE+1
ld bc, 767
ld (hl), TEXT_ATTR ; White background for text areas
ldir
ret
; ----------------------------------------------------------------------------
; Draw UI
; ----------------------------------------------------------------------------
; Draws score display and turn indicator
draw_ui:
call draw_scores
call draw_turn_indicator
ret
; ----------------------------------------------------------------------------
; Draw Scores
; ----------------------------------------------------------------------------
; Displays "P1: nn P2: nn" with player colours
draw_scores:
; Count cells for each player
call count_cells
; Draw P1 label "P1:"
ld b, SCORE_ROW
ld c, P1_SCORE_COL
ld a, 'P'
call print_char
inc c
ld a, '1'
call print_char
inc c
ld a, ':'
call print_char
inc c
; Print P1 score
ld a, (p1_count)
call print_two_digits
; Set P1 colour attribute
ld a, SCORE_ROW
ld c, P1_SCORE_COL
ld b, 5 ; "P1:nn" = 5 characters
ld e, P1_TEXT
call set_attr_range
; Draw P2 label "P2:"
ld b, SCORE_ROW
ld c, P2_SCORE_COL
ld a, 'P'
call print_char
inc c
ld a, '2'
call print_char
inc c
ld a, ':'
call print_char
inc c
; Print P2 score
ld a, (p2_count)
call print_two_digits
; Set P2 colour attribute
ld a, SCORE_ROW
ld c, P2_SCORE_COL
ld b, 5
ld e, P2_TEXT
call set_attr_range
ret
; ----------------------------------------------------------------------------
; Draw Turn Indicator
; ----------------------------------------------------------------------------
; Shows "TURN" with current player's colour
draw_turn_indicator:
; Print "TURN"
ld b, TURN_ROW
ld c, TURN_COL
ld a, 'T'
call print_char
inc c
ld a, 'U'
call print_char
inc c
ld a, 'R'
call print_char
inc c
ld a, 'N'
call print_char
; Set attribute based on current player
ld a, (current_player)
cp 1
jr z, .dti_p1
ld e, P2_TEXT
jr .dti_set
.dti_p1:
ld e, P1_TEXT
.dti_set:
ld a, TURN_ROW
ld c, TURN_COL
ld b, 4 ; "TURN" = 4 chars
call set_attr_range
ret
; ----------------------------------------------------------------------------
; Print Character
; ----------------------------------------------------------------------------
; A = ASCII character (32-127), B = row (0-23), C = column (0-31)
; Writes character directly to display file using ROM character set
print_char:
push bc
push de
push hl
push af
; Calculate character data address: CHAR_SET + char*8
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl ; HL = char * 8
ld de, CHAR_SET
add hl, de ; HL = source address
push hl ; Save character data address
; Calculate display file address
; Screen address: high byte varies with row, low byte = column
ld a, b ; A = row (0-23)
and %00011000 ; Get which third (0, 8, 16)
add a, $40 ; Add display file base high byte
ld d, a
ld a, b ; A = row
and %00000111 ; Get line within character row
rrca
rrca
rrca ; Shift to bits 5-7
add a, c ; Add column
ld e, a ; DE = screen address
pop hl ; HL = character data
; Copy 8 bytes (8 pixel rows of character)
ld b, 8
.pc_loop:
ld a, (hl)
ld (de), a
inc hl
inc d ; Next screen line (add 256)
djnz .pc_loop
pop af
pop hl
pop de
pop bc
ret
; ----------------------------------------------------------------------------
; Print Two Digits
; ----------------------------------------------------------------------------
; A = number (0-99), B = row, C = column (will advance by 2)
; Prints number as two digits
print_two_digits:
push bc
; Calculate tens digit
ld d, 0 ; Tens counter
.ptd_tens:
cp 10
jr c, .ptd_print
sub 10
inc d
jr .ptd_tens
.ptd_print:
push af ; Save units digit
; Print tens digit
ld a, d
add a, '0'
call print_char
inc c
; Print units digit
pop af
add a, '0'
call print_char
inc c
pop bc
ret
; ----------------------------------------------------------------------------
; Count Cells
; ----------------------------------------------------------------------------
; Counts cells owned by each player
count_cells:
xor a
ld (p1_count), a
ld (p2_count), a
ld hl, board_state
ld b, 64 ; 64 cells
.cc_loop:
ld a, (hl)
cp STATE_P1
jr nz, .cc_not_p1
ld a, (p1_count)
inc a
ld (p1_count), a
jr .cc_next
.cc_not_p1:
cp STATE_P2
jr nz, .cc_next
ld a, (p2_count)
inc a
ld (p2_count), a
.cc_next:
inc hl
djnz .cc_loop
ret
; ----------------------------------------------------------------------------
; Set Attribute Range
; ----------------------------------------------------------------------------
; A = row, C = start column, B = count, E = attribute
set_attr_range:
push bc
push de
; Calculate start address: ATTR_BASE + row*32 + col
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl ; HL = row * 32
ld a, c
add a, l
ld l, a
ld bc, ATTR_BASE
add hl, bc ; HL = attribute address
pop de ; E = attribute
pop bc ; B = count
.sar_loop:
ld (hl), e
inc hl
djnz .sar_loop
ret
; ----------------------------------------------------------------------------
; Update Border
; ----------------------------------------------------------------------------
update_border:
ld a, (current_player)
cp 1
jr z, .ub_p1
ld a, P2_BORDER
jr .ub_set
.ub_p1:
ld a, P1_BORDER
.ub_set:
out (KEY_PORT), a
ret
; ----------------------------------------------------------------------------
; Initialise Game State
; ----------------------------------------------------------------------------
init_game:
ld hl, board_state
ld b, 64
xor a
.ig_loop:
ld (hl), a
inc hl
djnz .ig_loop
ld a, 1
ld (current_player), a
xor a
ld (cursor_row), a
ld (cursor_col), a
ld (p1_count), a
ld (p2_count), a
ld (last_key), a ; No previous key
ld (key_timer), a ; No delay active
; Initialize AI timer
ld a, AI_DELAY
ld (ai_timer), a
ret
; ----------------------------------------------------------------------------
; Draw Board Border
; ----------------------------------------------------------------------------
draw_board_border:
ld c, BOARD_ROW-1
ld d, BOARD_COL-1
ld b, BOARD_SIZE+2
call draw_border_row
ld c, BOARD_ROW+BOARD_SIZE
ld d, BOARD_COL-1
ld b, BOARD_SIZE+2
call draw_border_row
ld c, BOARD_ROW
ld d, BOARD_COL-1
ld b, BOARD_SIZE
call draw_border_col
ld c, BOARD_ROW
ld d, BOARD_COL+BOARD_SIZE
ld b, BOARD_SIZE
call draw_border_col
ret
draw_border_row:
push bc
.dbr_loop:
push bc
push de
ld a, c
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld a, d
add a, l
ld l, a
ld bc, ATTR_BASE
add hl, bc
ld (hl), BORDER_ATTR
pop de
pop bc
inc d
djnz .dbr_loop
pop bc
ret
draw_border_col:
push bc
.dbc_loop:
push bc
push de
ld a, c
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld a, d
add a, l
ld l, a
ld bc, ATTR_BASE
add hl, bc
ld (hl), BORDER_ATTR
pop de
pop bc
inc c
djnz .dbc_loop
pop bc
ret
; ----------------------------------------------------------------------------
; Draw Board
; ----------------------------------------------------------------------------
draw_board:
ld b, BOARD_SIZE
ld c, BOARD_ROW
.db_row:
push bc
ld b, BOARD_SIZE
ld d, BOARD_COL
.db_col:
push bc
ld a, c
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld a, d
add a, l
ld l, a
ld bc, ATTR_BASE
add hl, bc
ld (hl), EMPTY_ATTR
pop bc
inc d
djnz .db_col
pop bc
inc c
djnz .db_row
ret
; ----------------------------------------------------------------------------
; Draw Cursor
; ----------------------------------------------------------------------------
draw_cursor:
call get_cell_state
cp STATE_P1
jr z, .dc_p1
cp STATE_P2
jr z, .dc_p2
ld a, CURSOR_ATTR
jr .dc_set
.dc_p1:
ld a, P1_CURSOR
jr .dc_set
.dc_p2:
ld a, P2_CURSOR
.dc_set:
push af
ld a, (cursor_row)
add a, BOARD_ROW
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld a, (cursor_col)
add a, BOARD_COL
add a, l
ld l, a
ld bc, ATTR_BASE
add hl, bc
pop af
ld (hl), a
ret
; ----------------------------------------------------------------------------
; Clear Cursor
; ----------------------------------------------------------------------------
clear_cursor:
call get_cell_state
cp STATE_P1
jr z, .clc_p1
cp STATE_P2
jr z, .clc_p2
ld a, EMPTY_ATTR
jr .clc_set
.clc_p1:
ld a, P1_ATTR
jr .clc_set
.clc_p2:
ld a, P2_ATTR
.clc_set:
push af
ld a, (cursor_row)
add a, BOARD_ROW
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld a, (cursor_col)
add a, BOARD_COL
add a, l
ld l, a
ld bc, ATTR_BASE
add hl, bc
pop af
ld (hl), a
ret
; ----------------------------------------------------------------------------
; Get Cell State
; ----------------------------------------------------------------------------
get_cell_state:
ld a, (cursor_row)
add a, a
add a, a
add a, a
ld hl, board_state
ld b, 0
ld c, a
add hl, bc
ld a, (cursor_col)
ld c, a
add hl, bc
ld a, (hl)
ret
; ----------------------------------------------------------------------------
; Read Keyboard
; ----------------------------------------------------------------------------
read_keyboard:
xor a
ld (key_pressed), a
ld a, ROW_QAOP
in a, (KEY_PORT)
bit 0, a
jr nz, .rk_not_q
ld a, 1
ld (key_pressed), a
ret
.rk_not_q:
ld a, ROW_ASDF
in a, (KEY_PORT)
bit 0, a
jr nz, .rk_not_a
ld a, 2
ld (key_pressed), a
ret
.rk_not_a:
ld a, ROW_YUIOP
in a, (KEY_PORT)
bit 1, a
jr nz, .rk_not_o
ld a, 3
ld (key_pressed), a
ret
.rk_not_o:
ld a, ROW_YUIOP
in a, (KEY_PORT)
bit 0, a
jr nz, .rk_not_p
ld a, 4
ld (key_pressed), a
ret
.rk_not_p:
ld a, ROW_SPACE
in a, (KEY_PORT)
bit 0, a
jr nz, .rk_not_space
ld a, 5
ld (key_pressed), a
.rk_not_space:
ret
; ----------------------------------------------------------------------------
; Handle Input
; ----------------------------------------------------------------------------
; Implements key repeat delay for smooth cursor movement
handle_input:
ld a, (key_pressed)
or a
jr nz, .hi_have_key
; No key pressed - reset tracking
xor a
ld (last_key), a
ld (key_timer), a
ret
.hi_have_key:
; Space (claim) always works immediately
cp 5
jr z, try_claim
; Check if same key as last frame
ld b, a ; Save current key
ld a, (last_key)
cp b
jr nz, .hi_new_key
; Same key - check timer
ld a, (key_timer)
or a
jr z, .hi_allow ; Timer expired, allow repeat
dec a
ld (key_timer), a
ret ; Still waiting
.hi_new_key:
; New key pressed - save it and reset timer
ld a, b
ld (last_key), a
ld a, KEY_DELAY
ld (key_timer), a
.hi_allow:
; Process movement
call clear_cursor
ld a, (key_pressed)
cp 1
jr nz, .hi_not_up
ld a, (cursor_row)
or a
jr z, .hi_done
dec a
ld (cursor_row), a
jr .hi_done
.hi_not_up:
cp 2
jr nz, .hi_not_down
ld a, (cursor_row)
cp BOARD_SIZE-1
jr z, .hi_done
inc a
ld (cursor_row), a
jr .hi_done
.hi_not_down:
cp 3
jr nz, .hi_not_left
ld a, (cursor_col)
or a
jr z, .hi_done
dec a
ld (cursor_col), a
jr .hi_done
.hi_not_left:
cp 4
jr nz, .hi_done
ld a, (cursor_col)
cp BOARD_SIZE-1
jr z, .hi_done
inc a
ld (cursor_col), a
.hi_done:
call draw_cursor
ret
; ----------------------------------------------------------------------------
; Try Claim Cell
; ----------------------------------------------------------------------------
try_claim:
call get_cell_state
or a
jr z, .tc_valid
; Cell already claimed - error feedback
call sound_error
call flash_border_error
call update_border ; Restore correct border colour
ret
.tc_valid:
; Valid move - claim the cell
call claim_cell
call sound_claim
ld a, (current_player)
xor 3
ld (current_player), a
call draw_ui ; Update scores and turn indicator
; Check if game is over
call check_game_over
or a
jr z, .tc_continue
; Game over - show results and return to title
call show_results
call victory_celebration
call wait_for_key
; Return to title screen
ld a, GS_TITLE
ld (game_state), a
call init_screen
call draw_title_screen
xor a
out (KEY_PORT), a ; Black border for title
ret
.tc_continue:
call update_border
call draw_cursor
ret
; ----------------------------------------------------------------------------
; Claim Cell
; ----------------------------------------------------------------------------
claim_cell:
ld a, (cursor_row)
add a, a
add a, a
add a, a
ld hl, board_state
ld b, 0
ld c, a
add hl, bc
ld a, (cursor_col)
ld c, a
add hl, bc
ld a, (current_player)
ld (hl), a
push af
ld a, (cursor_row)
add a, BOARD_ROW
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld a, (cursor_col)
add a, BOARD_COL
add a, l
ld l, a
ld bc, ATTR_BASE
add hl, bc
pop af
cp 1
jr z, .clm_is_p1
ld (hl), P2_ATTR
ret
.clm_is_p1:
ld (hl), P1_ATTR
ret
; ----------------------------------------------------------------------------
; Sound - Claim
; ----------------------------------------------------------------------------
sound_claim:
ld hl, 400
ld b, 20
.scl_loop:
push bc
push hl
ld b, h
ld c, l
.scl_tone:
ld a, $10
out (KEY_PORT), a
call .scl_delay
xor a
out (KEY_PORT), a
call .scl_delay
dec bc
ld a, b
or c
jr nz, .scl_tone
pop hl
pop bc
ld de, 20
or a
sbc hl, de
djnz .scl_loop
ret
.scl_delay:
push bc
ld b, 5
.scl_delay_loop:
djnz .scl_delay_loop
pop bc
ret
; ----------------------------------------------------------------------------
; Sound - Error
; ----------------------------------------------------------------------------
; Harsh buzz for invalid move
sound_error:
ld b, 30 ; Duration
.se_loop:
push bc
; Low frequency buzz (longer delay = lower pitch)
ld a, $10
out (KEY_PORT), a
ld c, 80 ; Longer delay for low pitch
.se_delay1:
dec c
jr nz, .se_delay1
xor a
out (KEY_PORT), a
ld c, 80
.se_delay2:
dec c
jr nz, .se_delay2
pop bc
djnz .se_loop
ret
; ----------------------------------------------------------------------------
; Flash Border Error
; ----------------------------------------------------------------------------
; Flash border red briefly to indicate error
flash_border_error:
; Flash red 3 times
ld b, 3
.fbe_loop:
push bc
; Red border
ld a, ERROR_BORDER
out (KEY_PORT), a
; Short delay (about 3 frames)
ld bc, 8000
.fbe_delay1:
dec bc
ld a, b
or c
jr nz, .fbe_delay1
; Black border (brief off)
xor a
out (KEY_PORT), a
; Short delay
ld bc, 4000
.fbe_delay2:
dec bc
ld a, b
or c
jr nz, .fbe_delay2
pop bc
djnz .fbe_loop
ret
; ----------------------------------------------------------------------------
; Check Game Over
; ----------------------------------------------------------------------------
; Returns A=1 if game is over (board full), A=0 otherwise
check_game_over:
; Game is over when p1_count + p2_count == 64
ld a, (p1_count)
ld b, a
ld a, (p2_count)
add a, b
cp TOTAL_CELLS
jr z, .cgo_over
xor a ; Not over
ret
.cgo_over:
ld a, 1 ; Game over
ret
; ----------------------------------------------------------------------------
; Show Results
; ----------------------------------------------------------------------------
; Displays winner message based on scores
show_results:
; Clear turn indicator
ld a, TURN_ROW
ld c, TURN_COL
ld b, 4
ld e, TEXT_ATTR
call set_attr_range
; Determine winner
ld a, (p1_count)
ld b, a
ld a, (p2_count)
cp b
jr c, .sr_p1_wins ; p2 < p1, so p1 wins
jr z, .sr_draw ; p1 == p2, draw
; p2 > p1, p2 wins
jr .sr_p2_wins
.sr_p1_wins:
; Display "P1 WINS!"
ld b, RESULT_ROW
ld c, RESULT_COL
ld hl, msg_p1_wins
ld e, P1_TEXT
call print_message
jr .sr_continue
.sr_p2_wins:
; Display "P2 WINS!"
ld b, RESULT_ROW
ld c, RESULT_COL
ld hl, msg_p2_wins
ld e, P2_TEXT
call print_message
jr .sr_continue
.sr_draw:
; Display "DRAW!"
ld b, RESULT_ROW
ld c, RESULT_COL + 2 ; Centre "DRAW!" better
ld hl, msg_draw
ld e, TEXT_ATTR
call print_message
.sr_continue:
; Display "PRESS ANY KEY" prompt
ld b, CONTINUE_ROW
ld c, CONTINUE_COL
ld hl, msg_continue
ld e, TEXT_ATTR
call print_message
ret
; ----------------------------------------------------------------------------
; Print Message
; ----------------------------------------------------------------------------
; HL = pointer to null-terminated string
; B = row, C = starting column, E = attribute for message area
print_message:
; Save parameters we need later
push de ; Save attribute in E
push bc ; Save row (B) and start column (C)
; Print characters
.pm_loop:
ld a, (hl)
or a
jr z, .pm_done
call print_char
inc hl
inc c
jr .pm_loop
.pm_done:
; C now has end column
; Calculate length: end_col - start_col
ld a, c ; A = end column
pop bc ; B = row, C = start column
sub c ; A = length
ld d, a ; D = length (save it)
; Set up for set_attr_range: A=row, C=start_col, B=count, E=attr
ld a, b ; A = row
ld b, d ; B = count (length)
pop de ; E = attribute
call set_attr_range
ret
; ----------------------------------------------------------------------------
; Victory Celebration
; ----------------------------------------------------------------------------
; Flashes border in winner's colour
victory_celebration:
; Determine winner's border colour
ld a, (p1_count)
ld b, a
ld a, (p2_count)
cp b
jr c, .vc_p1 ; p2 < p1
jr z, .vc_draw ; draw - use white
ld d, P2_BORDER ; p2 wins
jr .vc_flash
.vc_p1:
ld d, P1_BORDER
jr .vc_flash
.vc_draw:
ld d, 7 ; White for draw
.vc_flash:
; Flash border 5 times
ld b, 5
.vc_loop:
push bc
; Winner's colour
ld a, d
out (KEY_PORT), a
; Delay
ld bc, 15000
.vc_delay1:
dec bc
ld a, b
or c
jr nz, .vc_delay1
; Black
xor a
out (KEY_PORT), a
; Delay
ld bc, 10000
.vc_delay2:
dec bc
ld a, b
or c
jr nz, .vc_delay2
pop bc
djnz .vc_loop
ret
; ----------------------------------------------------------------------------
; Draw Title Screen
; ----------------------------------------------------------------------------
; Displays game title and prompt
draw_title_screen:
; Draw "INK WAR" title
ld b, TITLE_ROW
ld c, TITLE_COL
ld hl, msg_title
ld e, TEXT_ATTR
call print_message
; Draw "1 - TWO PLAYER"
ld b, MODE1_ROW
ld c, MODE1_COL
ld hl, msg_mode1
ld e, TEXT_ATTR
call print_message
; Draw "2 - VS COMPUTER"
ld b, MODE2_ROW
ld c, MODE2_COL
ld hl, msg_mode2
ld e, TEXT_ATTR
call print_message
ret
; ----------------------------------------------------------------------------
; Wait Key Release
; ----------------------------------------------------------------------------
; Waits until all keys are released
wait_key_release:
.wkr_loop:
xor a
in a, (KEY_PORT)
cpl ; Invert (keys are active low)
and %00011111 ; Mask to key bits
jr nz, .wkr_loop ; Still holding a key
ret
; ----------------------------------------------------------------------------
; Wait For Key
; ----------------------------------------------------------------------------
; Waits until any key is pressed
wait_for_key:
; First wait for all keys to be released
.wfk_release:
xor a
in a, (KEY_PORT)
cpl ; Invert (keys are active low)
and %00011111 ; Mask to key bits
jr nz, .wfk_release
; Now wait for a key press
.wfk_wait:
halt ; Wait for interrupt
xor a
in a, (KEY_PORT)
cpl
and %00011111
jr z, .wfk_wait
ret
; ----------------------------------------------------------------------------
; AI Make Move
; ----------------------------------------------------------------------------
; AI picks best adjacent cell (or random if none)
ai_make_move:
; Find best cell adjacent to AI territory
call find_best_adjacent_cell
; A = cell index (0-63), or $FF if board full
cp $ff
ret z ; No empty cells (shouldn't happen)
; Convert index to row/col and set cursor
ld b, a
and %00000111 ; Column = index AND 7
ld (cursor_col), a
ld a, b
rrca
rrca
rrca
and %00000111 ; Row = index >> 3
ld (cursor_row), a
; Claim the cell (reuse existing code)
call claim_cell
call sound_claim
; Switch player
ld a, (current_player)
xor 3
ld (current_player), a
call draw_ui
; Check if game is over
call check_game_over
or a
jr z, .aim_continue
; Game over - show results and return to title
call show_results
call victory_celebration
call wait_for_key
; Return to title screen
ld a, GS_TITLE
ld (game_state), a
call init_screen
call draw_title_screen
xor a
out (KEY_PORT), a ; Black border for title
ret
.aim_continue:
call update_border
call draw_cursor
ret
; ----------------------------------------------------------------------------
; Find Best Cell (Offense + Defense)
; ----------------------------------------------------------------------------
; Returns A = index of empty cell with best combined score, or $FF if none
; Score = adjacent AI cells (offense) + adjacent human cells (defense)
; This makes the AI both expand territory AND block the human
find_best_adjacent_cell:
; Initialize best tracking
ld a, $ff
ld (best_cell), a ; No best cell yet
xor a
ld (best_score), a ; Best score = 0
; Scan all 64 cells
ld c, 0 ; C = current cell index
.fbac_loop:
; Check if cell is empty
ld hl, board_state
ld d, 0
ld e, c
add hl, de
ld a, (hl)
or a
jr nz, .fbac_next ; Not empty, skip
; Empty cell - count adjacent AI cells (offense)
push bc
ld a, c
call count_adjacent_ai
ld b, a ; B = AI adjacent count
; Count adjacent human cells (defense)
ld a, c
call count_adjacent_p1
add a, b ; A = combined score (AI + P1)
pop bc
; Compare with best score
ld b, a ; B = this score
ld a, (best_score)
cp b
jr nc, .fbac_next ; Current best >= this score
; New best found
ld a, b
ld (best_score), a
ld a, c
ld (best_cell), a
.fbac_next:
inc c
ld a, c
cp 64
jr c, .fbac_loop ; Continue if c < 64
; Check if we found an adjacent cell
ld a, (best_score)
or a
jr z, .fbac_random ; No adjacent cells, use random
; Return best adjacent cell
ld a, (best_cell)
ret
.fbac_random:
; Fall back to random empty cell
call find_random_empty_cell
ret
best_cell: defb 0
best_score: defb 0
; ----------------------------------------------------------------------------
; Count Adjacent AI Cells
; ----------------------------------------------------------------------------
; A = cell index (0-63)
; Returns A = count of adjacent cells owned by AI (P2)
count_adjacent_ai:
ld (temp_cell), a
xor a
ld (adj_count), a
; Get row and column
ld a, (temp_cell)
ld b, a
and %00000111 ; Column
ld c, a
ld a, b
rrca
rrca
rrca
and %00000111 ; Row
ld b, a ; B = row, C = col
; Check up (row-1)
ld a, b
or a
jr z, .caa_skip_up ; Row 0, no up neighbor
dec a ; Row - 1
push bc
ld b, a
call .caa_check_cell
pop bc
.caa_skip_up:
; Check down (row+1)
ld a, b
cp 7
jr z, .caa_skip_down ; Row 7, no down neighbor
inc a ; Row + 1
push bc
ld b, a
call .caa_check_cell
pop bc
.caa_skip_down:
; Check left (col-1)
ld a, c
or a
jr z, .caa_skip_left ; Col 0, no left neighbor
dec a ; Col - 1
push bc
ld c, a
call .caa_check_cell
pop bc
.caa_skip_left:
; Check right (col+1)
ld a, c
cp 7
jr z, .caa_skip_right ; Col 7, no right neighbor
inc a ; Col + 1
push bc
ld c, a
call .caa_check_cell
pop bc
.caa_skip_right:
ld a, (adj_count)
ret
; Helper: check if cell at (B,C) is AI owned
.caa_check_cell:
; Calculate index: row*8 + col
ld a, b
rlca
rlca
rlca ; Row * 8
add a, c ; + col
ld hl, board_state
ld d, 0
ld e, a
add hl, de
ld a, (hl)
cp STATE_P2 ; AI is Player 2
ret nz ; Not AI cell
; AI cell - increment count
ld a, (adj_count)
inc a
ld (adj_count), a
ret
temp_cell: defb 0
adj_count: defb 0
; ----------------------------------------------------------------------------
; Count Adjacent Human Cells
; ----------------------------------------------------------------------------
; A = cell index (0-63)
; Returns A = count of adjacent cells owned by human (P1)
count_adjacent_p1:
ld (temp_cell), a
xor a
ld (adj_count), a
; Get row and column
ld a, (temp_cell)
ld b, a
and %00000111 ; Column
ld c, a
ld a, b
rrca
rrca
rrca
and %00000111 ; Row
ld b, a ; B = row, C = col
; Check up (row-1)
ld a, b
or a
jr z, .cap_skip_up ; Row 0, no up neighbor
dec a ; Row - 1
push bc
ld b, a
call .cap_check_cell
pop bc
.cap_skip_up:
; Check down (row+1)
ld a, b
cp 7
jr z, .cap_skip_down ; Row 7, no down neighbor
inc a ; Row + 1
push bc
ld b, a
call .cap_check_cell
pop bc
.cap_skip_down:
; Check left (col-1)
ld a, c
or a
jr z, .cap_skip_left ; Col 0, no left neighbor
dec a ; Col - 1
push bc
ld c, a
call .cap_check_cell
pop bc
.cap_skip_left:
; Check right (col+1)
ld a, c
cp 7
jr z, .cap_skip_right ; Col 7, no right neighbor
inc a ; Col + 1
push bc
ld c, a
call .cap_check_cell
pop bc
.cap_skip_right:
ld a, (adj_count)
ret
; Helper: check if cell at (B,C) is human owned
.cap_check_cell:
; Calculate index: row*8 + col
ld a, b
rlca
rlca
rlca ; Row * 8
add a, c ; + col
ld hl, board_state
ld d, 0
ld e, a
add hl, de
ld a, (hl)
cp STATE_P1 ; Human is Player 1
ret nz ; Not human cell
; Human cell - increment count
ld a, (adj_count)
inc a
ld (adj_count), a
ret
; ----------------------------------------------------------------------------
; Find Random Empty Cell
; ----------------------------------------------------------------------------
; Returns A = index of a random empty cell (0-63), or $FF if none
find_random_empty_cell:
; Get random starting position
call get_random
and %00111111 ; Limit to 0-63
ld c, a ; C = start index
ld b, 64 ; B = cells to check
.frec_loop:
; Check if cell at index C is empty
ld hl, board_state
ld d, 0
ld e, c
add hl, de
ld a, (hl)
or a
jr z, .frec_found ; Found empty cell
; Try next cell (wrap around)
inc c
ld a, c
and %00111111 ; Wrap at 64
ld c, a
djnz .frec_loop
; No empty cells found
ld a, $ff
ret
.frec_found:
ld a, c ; Return cell index
ret
; ----------------------------------------------------------------------------
; Get Random
; ----------------------------------------------------------------------------
; Returns A = pseudo-random number using R register
get_random:
ld a, r ; R register changes every instruction
ld b, a
ld a, (random_seed)
add a, b
rlca
xor b
ld (random_seed), a
ret
random_seed: defb $5a ; Seed value
; ----------------------------------------------------------------------------
; Messages
; ----------------------------------------------------------------------------
msg_p1_wins: defb "P1 WINS!", 0
msg_p2_wins: defb "P2 WINS!", 0
msg_draw: defb "DRAW!", 0
msg_title: defb "INK WAR", 0
msg_mode1: defb "1 - TWO PLAYER", 0
msg_mode2: defb "2 - VS COMPUTER", 0
msg_continue: defb "PRESS ANY KEY", 0
; ----------------------------------------------------------------------------
; Variables
; ----------------------------------------------------------------------------
game_state: defb 0 ; 0=title, 1=playing, 2=results
game_mode: defb 0 ; 0=two player, 1=vs AI
cursor_row: defb 0
cursor_col: defb 0
key_pressed: defb 0
last_key: defb 0 ; Previous frame's key for repeat detection
key_timer: defb 0 ; Countdown for key repeat delay
ai_timer: defb 0 ; Countdown before AI moves
current_player: defb 1
p1_count: defb 0
p2_count: defb 0
board_state: defs 64, 0
; ----------------------------------------------------------------------------
; End
; ----------------------------------------------------------------------------
end start
Try This: Defensive Weighting
Want the AI to prioritise blocking over expanding? Multiply the defense score:
; Count adjacent human cells (defense)
ld a, c
call count_adjacent_p1
add a, a ; Double the defense score
add a, b ; A = (P1 * 2) + AIThis makes blocking human territory twice as valuable as expanding AI territory.
Try This: Offense Weighting
Or prioritise expansion:
; Count adjacent AI cells (offense)
ld a, c
call count_adjacent_ai
add a, a ; Double the offense score
ld b, a
; Count adjacent human cells (defense)
ld a, c
call count_adjacent_p1
add a, b ; A = (AI * 2) + P1Different weightings create different AI personalities.
What You’ve Learnt
- Multi-factor evaluation — Combining multiple scores for better decisions
- Defense vs offense — Blocking as a strategic consideration
- Code reuse — New function mirrors existing one with minimal changes
- Emergent behaviour — Simple scoring creates complex strategy
What’s Next
In Unit 12, we’ll add corner and edge strategy — the AI will recognise that edges have fewer neighbours and corners are strategic positions.
What Changed
Unit 10 → Unit 11
+106-8
| 1 | 1 | ; ============================================================================ | |
| 2 | - | ; INK WAR - Unit 10: Smarter AI - Adjacent Priority | |
| 2 | + | ; INK WAR - Unit 11: Defensive AI | |
| 3 | 3 | ; ============================================================================ | |
| 4 | - | ; AI now prefers cells adjacent to its existing territory. Builds connected | |
| 5 | - | ; regions instead of scattered claims. Falls back to random if no adjacent. | |
| 4 | + | ; AI now considers both offense and defense. Scores cells by: | |
| 5 | + | ; - Adjacent AI cells (expansion) + Adjacent human cells (blocking) | |
| 6 | + | ; Blocks human territory growth while still building its own. | |
| 6 | 7 | ; | |
| 7 | 8 | ; Controls: Q=Up, A=Down, O=Left, P=Right, SPACE=Claim | |
| 8 | 9 | ; 1=Two Player, 2=vs Computer (on title screen) | |
| ... | |||
| 1437 | 1438 | ret | |
| 1438 | 1439 | | |
| 1439 | 1440 | ; ---------------------------------------------------------------------------- | |
| 1440 | - | ; Find Best Adjacent Cell | |
| 1441 | + | ; Find Best Cell (Offense + Defense) | |
| 1441 | 1442 | ; ---------------------------------------------------------------------------- | |
| 1442 | - | ; Returns A = index of empty cell with most AI neighbors, or $FF if none | |
| 1443 | - | ; Prefers cells adjacent to existing AI territory | |
| 1443 | + | ; Returns A = index of empty cell with best combined score, or $FF if none | |
| 1444 | + | ; Score = adjacent AI cells (offense) + adjacent human cells (defense) | |
| 1445 | + | ; This makes the AI both expand territory AND block the human | |
| 1444 | 1446 | | |
| 1445 | 1447 | find_best_adjacent_cell: | |
| 1446 | 1448 | ; Initialize best tracking | |
| ... | |||
| 1462 | 1464 | or a | |
| 1463 | 1465 | jr nz, .fbac_next ; Not empty, skip | |
| 1464 | 1466 | | |
| 1465 | - | ; Empty cell - count adjacent AI cells | |
| 1467 | + | ; Empty cell - count adjacent AI cells (offense) | |
| 1466 | 1468 | push bc | |
| 1467 | 1469 | ld a, c | |
| 1468 | 1470 | call count_adjacent_ai | |
| 1471 | + | ld b, a ; B = AI adjacent count | |
| 1472 | + | | |
| 1473 | + | ; Count adjacent human cells (defense) | |
| 1474 | + | ld a, c | |
| 1475 | + | call count_adjacent_p1 | |
| 1476 | + | add a, b ; A = combined score (AI + P1) | |
| 1469 | 1477 | pop bc | |
| 1470 | - | ; A = number of adjacent AI cells | |
| 1471 | 1478 | | |
| 1472 | 1479 | ; Compare with best score | |
| 1473 | 1480 | ld b, a ; B = this score | |
| ... | |||
| 1597 | 1604 | | |
| 1598 | 1605 | temp_cell: defb 0 | |
| 1599 | 1606 | adj_count: defb 0 | |
| 1607 | + | | |
| 1608 | + | ; ---------------------------------------------------------------------------- | |
| 1609 | + | ; Count Adjacent Human Cells | |
| 1610 | + | ; ---------------------------------------------------------------------------- | |
| 1611 | + | ; A = cell index (0-63) | |
| 1612 | + | ; Returns A = count of adjacent cells owned by human (P1) | |
| 1613 | + | | |
| 1614 | + | count_adjacent_p1: | |
| 1615 | + | ld (temp_cell), a | |
| 1616 | + | xor a | |
| 1617 | + | ld (adj_count), a | |
| 1618 | + | | |
| 1619 | + | ; Get row and column | |
| 1620 | + | ld a, (temp_cell) | |
| 1621 | + | ld b, a | |
| 1622 | + | and %00000111 ; Column | |
| 1623 | + | ld c, a | |
| 1624 | + | ld a, b | |
| 1625 | + | rrca | |
| 1626 | + | rrca | |
| 1627 | + | rrca | |
| 1628 | + | and %00000111 ; Row | |
| 1629 | + | ld b, a ; B = row, C = col | |
| 1630 | + | | |
| 1631 | + | ; Check up (row-1) | |
| 1632 | + | ld a, b | |
| 1633 | + | or a | |
| 1634 | + | jr z, .cap_skip_up ; Row 0, no up neighbor | |
| 1635 | + | dec a ; Row - 1 | |
| 1636 | + | push bc | |
| 1637 | + | ld b, a | |
| 1638 | + | call .cap_check_cell | |
| 1639 | + | pop bc | |
| 1640 | + | .cap_skip_up: | |
| 1641 | + | | |
| 1642 | + | ; Check down (row+1) | |
| 1643 | + | ld a, b | |
| 1644 | + | cp 7 | |
| 1645 | + | jr z, .cap_skip_down ; Row 7, no down neighbor | |
| 1646 | + | inc a ; Row + 1 | |
| 1647 | + | push bc | |
| 1648 | + | ld b, a | |
| 1649 | + | call .cap_check_cell | |
| 1650 | + | pop bc | |
| 1651 | + | .cap_skip_down: | |
| 1652 | + | | |
| 1653 | + | ; Check left (col-1) | |
| 1654 | + | ld a, c | |
| 1655 | + | or a | |
| 1656 | + | jr z, .cap_skip_left ; Col 0, no left neighbor | |
| 1657 | + | dec a ; Col - 1 | |
| 1658 | + | push bc | |
| 1659 | + | ld c, a | |
| 1660 | + | call .cap_check_cell | |
| 1661 | + | pop bc | |
| 1662 | + | .cap_skip_left: | |
| 1663 | + | | |
| 1664 | + | ; Check right (col+1) | |
| 1665 | + | ld a, c | |
| 1666 | + | cp 7 | |
| 1667 | + | jr z, .cap_skip_right ; Col 7, no right neighbor | |
| 1668 | + | inc a ; Col + 1 | |
| 1669 | + | push bc | |
| 1670 | + | ld c, a | |
| 1671 | + | call .cap_check_cell | |
| 1672 | + | pop bc | |
| 1673 | + | .cap_skip_right: | |
| 1674 | + | | |
| 1675 | + | ld a, (adj_count) | |
| 1676 | + | ret | |
| 1677 | + | | |
| 1678 | + | ; Helper: check if cell at (B,C) is human owned | |
| 1679 | + | .cap_check_cell: | |
| 1680 | + | ; Calculate index: row*8 + col | |
| 1681 | + | ld a, b | |
| 1682 | + | rlca | |
| 1683 | + | rlca | |
| 1684 | + | rlca ; Row * 8 | |
| 1685 | + | add a, c ; + col | |
| 1686 | + | ld hl, board_state | |
| 1687 | + | ld d, 0 | |
| 1688 | + | ld e, a | |
| 1689 | + | add hl, de | |
| 1690 | + | ld a, (hl) | |
| 1691 | + | cp STATE_P1 ; Human is Player 1 | |
| 1692 | + | ret nz ; Not human cell | |
| 1693 | + | ; Human cell - increment count | |
| 1694 | + | ld a, (adj_count) | |
| 1695 | + | inc a | |
| 1696 | + | ld (adj_count), a | |
| 1697 | + | ret | |
| 1600 | 1698 | | |
| 1601 | 1699 | ; ---------------------------------------------------------------------------- | |
| 1602 | 1700 | ; Find Random Empty Cell |