[BITS 16]
[ORG 0x7C00]

cli

jmp start

balldir_x: db 0
balldir_y: db 0
ballpos: dw ((10 * 80) + 40)

draw:
	mov word [ds:ebx+eax*2], dx
	ret

drawbar:
	call draw

	inc ax

	cmp ax, cx
	jnz drawbar
	
	mov cx, ax
	add cx, 80
	ret

start:
	mov ebx, 0x0B8000

blankscreen:
	xor ax, ax
	mov cx, 0x0800
	mov dx, 0x0000

blankscreen_loop:
	call draw
	
	inc ax
	
	cmp ax, cx
	jnz blankscreen_loop

drawbars:
	xor ax, ax
	mov cx, 80
	mov dx, 0x20 | (1 << 12)
	call drawbar
	
	mov dx, 0x20 | (2 << 12)
	call drawbar
	
	mov dx, 0x20 | (4 << 12)
	call drawbar

logicloop:
	mov ax, [ballpos]
	mov dx, 0x20 | (15 << 12)
	call draw
	
	call ballcalc
	
	cmp ax, 0
	jg no_xrico
	call ricochet
no_xrico:
	
	cmp ax, 40 * 80
	jl no_yrico
	call ricochet
no_yrico:
	
	mov [ballpos], ax
	
	mov dx, 0x20 | (15 << 12)
	call draw
	
	jmp logicloop

ballcalc:
	mov cx, [balldir_y]
	add ax, cx
	sub ax, 80
	
	add al, [balldir_x]
	add ax, cx
	sub ax, 1
	
	ret

ricochet:
	mov dx, [balldir_y]
	xor dx, 160
	mov [balldir_y], dx
	
	mov dx, [balldir_x]
	xor dx, 2
	mov [balldir_x], dx
	
	ret