Trixter at 20:26, 14 August 2016

2016-08-14T20:26:52Z

Trixter at 19:47, 14 August 2016

2016-08-14T19:47:30Z

Trixter: Created page with "(Case study forthcoming) ; * ** %%% ### 4is256 ; * % @@@@ % # a 256-byte brick game ; %% # == @@ by Rrrola ; % ===..."

2016-08-14T18:46:29Z

Created page with "(Case study forthcoming) <syntaxhighlight lang=nasm> ; * ** %%% ### 4is256 ; * % @@@@ ** % # a 256-byte brick game ; **%% # == @@ by Rrrola ; % ===..."

New page

(Case study forthcoming)

<syntaxhighlight lang=nasm>
; * ** %%% ### 4is256
; * % @@@@ ** % # a 256-byte brick game
; **%% # == @@ by Rrrola
; % ==== ### == @@ <rrrola@gmail.com>

; STORY
; confused bricks fall down the pit of sorrow
; show them the rightful way of flawless rows
; make them complete
; make them disappear in joy
; and get awarded for their redemption

; CONTROLS AND SHIFTS
; left shift ......... move left
; right shift ....... move right
; ctrl .............. rotate ccw
; alt .............. fall faster

; SCORING
; fast falling ........... 1/row
; deleted rows ... 32/96/160/224
; don't delete too fast ... -256 (punishment for the greedy ;-))

; LEVEL (FALLING SPEED)
; increases every (1<<level) deletions

; note: needs vertical retrace for timing (fullscreen or pure DOS)
; greets to everyone who JUST WOULDN'T GET THE STRAIGHT ONE OMGWTF

HEIGHT equ 24 ; must be a multiple of 4
WIDTH equ 10 ; 4..23
PIT_CHAR equ 'º'
BRICK_CHAR equ 'Û'

org 100h ; assume ax=0 bl=0 sp=0FFFEh

inc ax
int 10h
mov ah,5 ; textmode 40x25, page 1 (offset 800h)
int 10h ; filled with gray spaces on black (0720h)
push word 0B800h
pop es
push es
pop ds

; Draw the pit and erase complete rows

P:
mov di,2178+(HEIGHT-1)*80
mov si,di ;-) si = source row, di = destination row
mov cx,HEIGHT+4
E:
sub di,byte 80
N:
add bl,64 ; score += {0,64,128,192}[erased rows mod 4]
sub si,byte 80+WIDTH*2

mov ax,800h+PIT_CHAR
stosw
sub di,byte WIDTH*2+4
stosw

mov dx,WIDTH
A:
or [di+(HEIGHT+4)*80+1],ah
and al,[si+1]
movsw ; white score at the bottom of the pit, shift rows
dec dx
jnz A

and al,8 ; brightness all the way?
jnz N
loop E

cmp si,di ; if any rows were deleted, adjust score to +32/96/160/224
je G
sub bl,32
dec sp ; sp = 0FFFEh-total deletions

; Generate a new brick

G: ; di=6F2h cx=0
in al,40h; could be "rdtsc" for hardcore randomness
mov ah,5Ah
mul di ; dx:ax=2711400h..277FF0Eh
mov bp,dx
mov cl,[byte bp-271h+S]
mov di,800h-160+48-(WIDTH|1)
mov si,es ;-) the highest bits of si need to be "10"

; bp = brick index + 271h
; cx = rotated brick layout (4 bits per row)
; di = brick position
; most significant zero bit in sp = number of frames before dropping
; (si is used for checking that)

; Increase the displayed score by 1

M:
or bl,bl
jz V
push di ; di = behind the last zero
mov di,800h+HEIGHT*80+50
dec bx
D:
dec di ; next digit
dec di
mov al,'0'; assume overflow
xchg al,[di]
or al,10h
cmp al,'9'
je D
inc ax
stosb ; if the digit wasn't '9', raise it
pop di

; Wait for vertical retrace start (70/sec) and erase the brick

V:
mov dx,3DAh
in al,dx
and al,8
jz V
W:
in al,dx
and al,8
jnz W ; al=0
call B ; if not erasable (= has no space to appear), GAME OVER
jnc near 0

; Keyboard handler

mov ah,2
int 16h
and bh,al ; bh = previous shift state
xchg al,bh
not bh ; if a shift was just pressed, set a bit in al

pusha

shr al,1 ; RSHIFT: X++
jnc X
scasw ; di+=2
X:

shr al,1 ; LSHIFT: X--
jnc Y
dec di
dec di
Y:

shl ax,15

jnc F ; ALT: Y++, score++
inc bx
mov bh,8 ; can be held until landing
H:
mov si,sp
add si,byte 16
add di,byte 80
F:

jns C ; CTRL: rotation
R: ; ax=8000h, CF=0
rcl cx,13 ; ax = cx rotated 90 degress ccw around [1;1]
rcr ax,1
jnc R
cmp ah,[byte bp-271h+S]
je I ; if we reach the original shape, reload (for O,S,Z)
ror ax,12
I:
xchg ah,al
xchg ax,cx
C: ; al=0

; Test whether changes were OK, drop if it's time

call B
jnc Q
add sp,byte 16
pusha
Q:
popa ; use [bp-7*16] for black background instead of gray
lea ax,[bp+0]
rol si,1 ; OF = (CF!=sign(si))
jnc L ; you can't land with alt only (less mistakes)

push word M
jno B ; doesn't have to fall: draw the brick

pop ax ; has to fall: clean the stack
xor ax,ax
pusha
jmp short H

L:
or al,8 ; draw the fallen brick bright and generate next brick
push word P

; Brick drawing (al=color cx=shape di=address)

B:
push bx
xor bx,bx
T:
ror cx,1
jnc skip ; brightness prevents drawing
test byte[bx+di],8 ; CF=0
jnz O
mov [bx+di],al
mov byte[bx+di-1],BRICK_CHAR
skip:
inc bx
inc bx ; bl:00 02 04 06 08
test bl,8 ; 50 52 54 56 58
jz T ; A0 A2 A4 A6 A8
add bl,72 ; F0 F2 F4 F6 F8 40+CF
jnc T
O:
pop bx ; if the brick could be drawn, CF=1
ret

; .... ##.. ..#. #... .##. .#.. ##..
; #### .##. ###. ###. ##.. ###. ##..
S: db 0F0h, 63h, 74h, 71h, 36h, 72h, 33h

</syntaxhighlight>

← Older revision		Revision as of 20:26, 14 August 2016
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	{{Tinyprog\|title=4is256\|author=Rrrola\|bsize=256\|link=http://www.pouet.net/prod.php?which=29286}}		{{Tinyprog\|title=4is256\|author=Rrrola\|bsize=256\|link=http://www.pouet.net/prod.php?which=29286}}
		+	[[Category:Case Study]]

	(Case study forthcoming)		(Case study forthcoming)

← Older revision		Revision as of 19:47, 14 August 2016
Line 1:		Line 1:
		+	{{Tinyprog\|title=4is256\|author=Rrrola\|bsize=256\|link=http://www.pouet.net/prod.php?which=29286}}
		+
	(Case study forthcoming)		(Case study forthcoming)

4is256 - Revision history

Trixter at 20:26, 14 August 2016

Trixter at 19:47, 14 August 2016

Trixter: Created page with "(Case study forthcoming) ; * ** %%% ### 4is256 ; * % @@@@ ** % # a 256-byte brick game ; **%% # == @@ by Rrrola ; % ===..."

Trixter: Created page with "(Case study forthcoming) ; * ** %%% ### 4is256 ; * % @@@@ % # a 256-byte brick game ; %% # == @@ by Rrrola ; % ===..."