Fontána by Řrřola [web]
; FON , ; TA ; N ; A ; a 128-byte intro by rrrola <[email protected]> ; greets to everyone who waits for the glitchy part ; DS (old) and ES (new) are arrays of max 16384 particles. ; Each particle is stored in 4 bytes: { s16 Y; s8 dY,dX; }; ; If Y==0, the particle is uninitialized (also implies dX:dY==0). ; X is the address - there's only one particle per column. ;TODO: backbuffer could be ss, saves fs: prefix with [bp+di] ; do I even need a backbuffer? ; swap+clear could be copy+clear org 100h ; assume ax=bx=0 cl=0xFF si=0x100 sp=di=-2 dx=cs<=0x50E4 les cx,[si+2] ; particles1: es=0x7B64 cx=0x8E02 ; C4 4C 02 mov fs,[byte si+E-100h] ; backbuffer: fs=0x60E4 ; 8E 64 7B lds bp,[si] ; particles2: ds=0x8E02 bp=0x4CC4 rep stosw ; clear particles1 mov al,13h int 10h ; 320x200, 256 colors ;main loop: add a new particle ; al=keypress M:mov ax,0xBDF9 ; steady stream xor di,di ; X=0 (center) Y=0xBDF9 (near the visible top) stosw ; dY=0xF9 (slightly up) dX=0xBD (left) ;swap+clear particles1 and 2, copy+clear backbuffer ; di=2 push es C:stosw ; clear particles2 (first pass: new particle's dX:dY) push 0xA000 pop es ; screen: es = 0xA000 xchg ax,[fs:di] stosw ; copy backbuffer to screen and clear it dec di dec di push ds pop es mov ax,bx ;0 jnz C ;flags from "dec di" pop ds ;for all particles1: ; si=X=index P:mov di,si ; di=X lodsw or ax,ax ; ax=Y; if ==0, skip (uninitialized) jz S ; (the dX:dY part is skipped next cycle) ; - add gravity mov cx,0x0908 ; ch = color = blue, cl=8 inc word[si] ; dY++, can overflow to dX ; - for each neighbor: pull particle up ; bx=0 mov bl,256-2 ; bx = Xdiff; look only to the right R:push ax sub ax,[si+bx] ; ax = Ydiff = Y-Y2 cmp ax,[di] ; if Ydiff==Y, skip (uninitialized) je F or ah,ah ; if Ydiff>256, skip (too far) jnz F mov ch,0xF ; pull up: color = white dec word[si] ; dY--, can overflow to dX F:add bx,sp ;-4 pop ax jns R ; - move particle, bounce if needed ; bx=-2 X:xchg ax,di ; 2 passes: first X, then Y ror word[si],cl; swap bytes xchg ax,bp mov al,8 imul byte[si] add ax,bp ; X += 8*dX, Y += 8*dY jno B mov al,[si] ; bounce, lose 1/4 speed sar byte[si],2 sub [si],al xchg ax,bp ; restore old position B:inc bx jnz X ; - find a free column, store new position and speed ; bx=0 H:scasw ; X+=4; X was already quantized to 4 bytes scasw cmp [es:di],bx jnz H ; repeat until column is free stosw ; store new Y movsw ; store new dX:dY ; - plot particle sar ax,cl ; ax = Yscreen (-128..127) imul bp,ax,320 ; bp = Yadr sar di,cl ; di = Xadr = Xscreen (-128..127) mov [fs:bp+di+320*(100-28)+160],ch ; ch = blue or white S:or si,si ; ah=0 if skipped (unitialized) jnz P ;esc? E:in al,60h ; E4 60 dec ax jnz M ret
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