# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1496872881 -10800
# Node ID 48755f08211ac81d562fb7d0112e87ca63d324ca
# Parent  81facff3a8ae7a4b84db8c146a4cdcb903cb9b51
move a block around

diff -r 81facff3a8ae -r 48755f08211a boot.asm
--- a/boot.asm	Wed Jun 07 08:56:42 2017 +0300
+++ b/boot.asm	Thu Jun 08 01:01:21 2017 +0300
@@ -1,16 +1,122 @@
+	xcells equ 40
+	ycells equ 25
+	poffs equ xcells * ycells
+	doffs equ poffs + 2
+	ticks_offs equ doffs + 2
+
+	key_w equ 17
+	key_a equ 30
+	key_s equ 31
+	key_d equ 32
+
+	org 0x7c00
 start:
 	mov ax, 0x13
 	int 0x10
+
+	push word 0x7e00
+	pop es
+	xor ax, ax
+	xor di, di
+	mov cx, 0xfffe
+	rep stosw
+	push es
+	pop ds   ; cells table segment -> ds
+
+	; init position
+	mov [si + poffs + 1], byte xcells / 2
+	mov [si + poffs], byte ycells / 2
+
 	push word 0xa000
 	pop es
 
 mainloop:
+	; keyboard input
+	push si
+	add si, doffs
+	in al, 0x60
+	cmp al, key_s
+	jnz .not_s
+	mov [si], word 1
+.not_s: cmp al, key_w
+	jnz .not_w
+	mov [si], word 0x00ff
+.not_w:
+	cmp al, key_d
+	jnz .not_d
+	mov [si], word 0x100
+.not_d: cmp al, key_a
+	jnz .endkey
+	mov [si], word 0xff00
+.endkey:
+	pop si
+
+	; clear screen
+	xor ax, ax
 	xor di, di
-	mov ax, 0x0202
 	mov cx, 32000
 	rep stosw
 
+	mov ax, [si + poffs]	; grab position
+
+	mov cx, [si + ticks_offs]
+	inc cx
+	and cx, 0x3ff
+	jnz .skip_move		; only move every 64 vsyncs
+
+	; move
+	add ah, [si + doffs + 1]
+	jnz .xnot0
+	neg byte [si + doffs + 1]
+.xnot0:	cmp ah, xcells - 1
+	jnz .xnotmax
+	neg byte [si + doffs + 1]
+.xnotmax:
+	add al, [si + doffs]
+	jnz .ynot0
+	neg byte [si + doffs]
+.ynot0:	cmp al, ycells
+	jnz .ynotmax
+	neg byte [si + doffs]
+.ynotmax:
+	mov [si + poffs], ax
+.skip_move:
+	mov [si + ticks_offs], cx
+
+	call draw_block
+
+
+	; wait vsync
+	mov dx, 0x3da
+.vbwait:in al, dx
+	and al, 8
+	jz .vbwait
 	jmp mainloop
 
+; ah: x, al: y
+draw_block:
+	push ax
+	xor al, al
+	shr ax, 5
+	mov di, ax
+
+	pop ax
+	xor ah, ah
+	shl ax, 3
+	mov bx, 320
+	mul bx
+	add di, ax
+	mov cx, 6
+.sline:
+	add di, 320
+	mov eax, 0x0f0f0f00
+	stosd
+	shr eax, 8
+	stosd
+	sub di, 8
+	dec cx
+	jnz .sline
+	ret
+
 	resb 510 - ($ - start)
 	db 0x55, 0xaa