; Copyright (C) 1995-2002 Justin Frankel
; Switches to 320x200, generates a pattern, and does palette cycling.
; Assemble with NASM.

[org 100h]
[segment .text]

  mov al, 13h
  int 10h

  mov bh, 0A0h
  mov es, bx

  mov al, 200
@ScreenLoopY:
  mov cx, 320
@ScreenLoopX:
  xor ax, cx
  stosb
  xor ax, cx
  loop @ScreenLoopX
  dec ax
  jnz @ScreenLoopY

@KeyLoop:
  mov dx, 03DAh
@VWait:
  in al, dx
  and al, 8
  jz @VWait

  dec bp

  mov dx, 3C8h
  mov ax, bp
  out dx, al 
  inc dx

  mov cl, 64
  mov di, 0FFh
  sub bx, bx
  mov si, 3Fh
@PaletteGenLoop1:
  inc di
  mov ax, si
  out dx, al
  mov ax, di
  out dx, al
  mov ax, bx
  out dx, al
  loop @PaletteGenLoop1

  mov cl, 64
  inc si
@PaletteGenLoop2:
  dec si
  mov ax, si
  out dx, al
  mov ax, di
  out dx, al
  mov ax, bx
  out dx, al
  loop @PaletteGenLoop2

  mov cl, 64
@PaletteGenLoop3:
  mov ax, si
  out dx, al
  mov ax, di
  out dx, al
  mov ax, bx
  out dx, al
  dec di
  inc bx
  loop @PaletteGenLoop3
  
  mov cl, 64
  inc di
@PaletteGenLoop4:
  mov ax, si
  out dx, al
  mov ax, di
  out dx, al
  dec bx
  mov ax, bx
  out dx, al
  inc si
  loop @PaletteGenLoop4

  mov ah, 1
  int 16h
  jz @KeyLoop

  mov ax, 3
  int 10h
  ret

END