INT 33 mouse demo

Back in the middle of 2008 I made something similar. White dot that remembers the background pixel. LMB is one color, RMB is another, Both together is the mix of the two.

Very unoptimized code, was just a personal test:
Assembles to 154 bytes.

Code:

org 100h

push 0a000h
pop es

mov ax,13h
int 10h

start:
call vsync1
call mouse

key:
mov ax,0c00h
int 21h
in al,60h
dec al
jnz start
mov ax,03h
int 10h
ret

mouse:
        mov al,[temp1]
        mov di,[temp2]
        stosb
        mov ax,03h
        int 33h
        shr cx,1h
        cmp bx,1h
        je col1
        cmp bx,2h
        je col2
        cmp bx,3h
        je col3
        mov ax,dx
        shl ax,8h
        shl dx,6h
        add ax,dx
        mov di,ax
        add di,cx
        mov al,[es:di]
        mov [temp1],al
        mov [temp2],di
        mov al,0fh
        stosb
        ret
        col1:
        mov [color],1
        jmp mouse1
        col2:
        mov [color],2
        jmp mouse1
        col3:
        mov [color],3
        mouse1:
        mov ax,dx
        shl ax,8h
        shl dx,6h
        add ax,dx
        mov di,ax
        add di,cx
        mov al,0fh
        mov [temp2],di
        mov bl,[color]
        mov [temp1],bl
        stosb
        ret


vsync1:
        pusha
        mov dx,3dah
vsync:
        in al,dx
        and al,8
        jz vsync
        popa
        ret

temp1 db 0
temp2 dw 0
color db 0

Edit:
Included a drawing I made. I doubled the size of the picture to make it more easily seen.
The drawing is bad, I can't draw good on a computer and the resolution didnt help much.