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c747c79 Oct 4, 2016
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325 lines (294 sloc) 8.29 KB
; Tetris
org 7c00h
; ==============================================================================
; DEBUGGING MACROS
; ==============================================================================
%ifdef DEBUG
%include "debug_macros.asm"
%endif
; ==============================================================================
; MACROS
; ==============================================================================
; Sleeps for the given number of microseconds.
%macro sleep 1
pusha
xor cx, cx
mov dx, %1
mov ah, 0x86
int 0x15
popa
%endmacro
; Choose a brick at random.
%macro select_brick 0
mov ah, 2 ; get current time
int 0x1a
mov al, byte [seed_value]
xor ax, dx
mov bl, 31
mul bx
inc ax
mov byte [seed_value], al
xor dx, dx
mov bx, 7
div bx
shl dl, 3
xchg ax, dx ; mov al, dl
%endmacro
; Sets video mode and hides cursor.
%macro clear_screen 0
xor ax, ax ; clear screen (40x25)
int 0x10
mov ah, 1 ; hide cursor
mov cx, 0x2607
int 0x10
%endmacro
field_left_col: equ 13
field_width: equ 14
inner_width: equ 12
inner_first_col: equ 14
start_row_col: equ 0x0412
%macro init_screen 0
clear_screen
mov dh, 3 ; row
mov cx, 18 ; number of rows
ia: push cx
inc dh ; increment row
mov dl, field_left_col ; set column
mov cx, field_width ; width of box
mov bx, 0x78 ; color
call set_and_write
cmp dh, 21 ; don't remove last line
je ib ; if last line jump
inc dx ; increase column
mov cx, inner_width ; width of box
xor bx, bx ; color
call set_and_write
ib: pop cx
loop ia
%endmacro
; ==============================================================================
delay: equ 0x7f00
seed_value: equ 0x7f02
section .text
start_tetris:
xor ax, ax
mov ds, ax
init_screen
new_brick:
mov byte [delay], 100 ; 3 * 100 = 300ms
select_brick ; returns the selected brick in AL
mov dx, start_row_col ; start at row 4 and col 38
lp:
call check_collision
jne $ ; collision -> game over
call print_brick
wait_or_keyboard:
xor cx, cx
mov cl, byte [delay]
wait_a:
push cx
sleep 3000 ; wait 3ms
push ax
mov ah, 1 ; check for keystroke; AX modified
int 0x16 ; http://www.ctyme.com/intr/rb-1755.htm
mov cx, ax
pop ax
jz no_key ; no keystroke
call clear_brick
; 4b left, 48 up, 4d right, 50 down
cmp ch, 0x4b ; left arrow
je left_arrow ; http://stackoverflow.com/questions/16939449/how-to-detect-arrow-keys-in-assembly
cmp ch, 0x48 ; up arrow
je up_arrow
cmp ch, 0x4d
je right_arrow
mov byte [delay], 10 ; every other key is fast down
jmp clear_keys
left_arrow:
dec dx
call check_collision
je clear_keys ; no collision
inc dx
jmp clear_keys
right_arrow:
inc dx
call check_collision
je clear_keys ; no collision
dec dx
jmp clear_keys
up_arrow:
mov bl, al
inc ax
inc ax
test al, 00000111b ; check for overflow
jnz nf ; no overflow
sub al, 8
nf: call check_collision
je clear_keys ; no collision
mov al, bl
clear_keys:
call print_brick
push ax
xor ah, ah ; remove key from buffer
int 0x16
pop ax
no_key:
pop cx
loop wait_a
call clear_brick
inc dh ; increase row
call check_collision
je lp ; no collision
dec dh
call print_brick
call check_filled
jmp new_brick
; ------------------------------------------------------------------------------
set_and_write:
mov ah, 2 ; set cursor
int 0x10
mov ax, 0x0920 ; write boxes
int 0x10
ret
set_and_read:
mov ah, 2 ; set cursor position
int 0x10
mov ah, 8 ; read character and attribute, BH = 0
int 0x10 ; result in AX
ret
; ------------------------------------------------------------------------------
; DH = current row
%macro replace_current_row 0
pusha ; replace current row with row above
mov dl, inner_first_col
mov cx, inner_width
cf_aa:
push cx
dec dh ; decrement row
call set_and_read
inc dh ; increment row
mov bl, ah ; color from AH to BL
mov cl, 1
call set_and_write
inc dx ; next column
pop cx
loop cf_aa
popa
%endmacro
check_filled:
pusha
mov dh, 21 ; start at row 21
next_row:
dec dh ; decrement row
jz cf_done ; at row 0 we are done
xor bx, bx
mov cx, inner_width
mov dl, inner_first_col ; start at first inner column
cf_loop:
call set_and_read
shr ah, 4 ; rotate to get background color in AH
jz cf_is_zero ; jmp if background color is 0
inc bx ; increment counter
inc dx ; go to next column
cf_is_zero:
loop cf_loop
cmp bl, inner_width ; if counter is 12 full we found a full row
jne next_row
replace_next_row: ; replace current row with rows above
replace_current_row
dec dh ; replace row above ... and so on
jnz replace_next_row
call check_filled ; check for other full rows
cf_done:
popa
ret
clear_brick:
xor bx, bx
jmp print_brick_no_color
print_brick: ; al = 0AAAARR0
mov bl, al ; select the right color
shr bl, 3
inc bx
shl bl, 4
print_brick_no_color:
inc bx ; set least significant bit
mov di, bx
jmp check_collision_main
; BL = color of brick
; DX = position (DH = row), AL = brick offset
; return: flag
check_collision:
mov di, 0
check_collision_main: ; DI = 1 -> check, 0 -> print
pusha
xor bx, bx ; load the brick into AX
mov bl, al
mov ax, word [bricks + bx]
xor bx, bx ; BH = page number, BL = collision counter
mov cx, 4
cc:
push cx
mov cl, 4
zz:
test ah, 10000000b
jz is_zero
push ax
or di, di
jz ee ; we just want to check for collisions
pusha ; print space with color stored in DI
mov bx, di ; at position in DX
xor al, al
mov cx, 1
call set_and_write
popa
jmp is_zero_a
ee:
call set_and_read
shr ah, 4 ; rotate to get background color in AH
jz is_zero_a ; jmp if background color is 0
inc bx
is_zero_a:
pop ax
is_zero:
shl ax, 1 ; move to next bit in brick mask
inc dx ; move to next column
loop zz
sub dl, 4 ; reset column
inc dh ; move to next row
pop cx
loop cc
or bl, bl ; bl != 0 -> collision
popa
ret
; ==============================================================================
bricks:
; in AL in AH
; 3rd + 4th 1st + 2nd row
db 01000100b, 01000100b, 00000000b, 11110000b
db 01000100b, 01000100b, 00000000b, 11110000b
db 01100000b, 00100010b, 00000000b, 11100010b
db 01000000b, 01100100b, 00000000b, 10001110b
db 01100000b, 01000100b, 00000000b, 00101110b
db 00100000b, 01100010b, 00000000b, 11101000b
db 00000000b, 01100110b, 00000000b, 01100110b
db 00000000b, 01100110b, 00000000b, 01100110b
db 00000000b, 11000110b, 01000000b, 00100110b
db 00000000b, 11000110b, 01000000b, 00100110b
db 00000000b, 01001110b, 01000000b, 01001100b
db 00000000b, 11100100b, 10000000b, 10001100b
db 00000000b, 01101100b, 01000000b, 10001100b
db 00000000b, 01101100b, 01000000b, 10001100b
%ifndef DEBUG
; It seems that I need a dummy partition table entry for my notebook.
times 446-($-$$) db 0
db 0x80 ; bootable
db 0x00, 0x01, 0x00 ; start CHS address
db 0x17 ; partition type
db 0x00, 0x02, 0x00 ; end CHS address
db 0x00, 0x00, 0x00, 0x00 ; LBA
db 0x02, 0x00, 0x00, 0x00 ; number of sectors
; At the end we need the boot sector signature.
times 510-($-$$) db 0
db 0x55
db 0xaa
%endif