fixed the speed in vertical motion of lovebug

diff --git a/bb.asm b/bb.asm
index c28880e..743dc9f 100644 (file)
--- a/bb.asm
+++ b/bb.asm
@@ -177,6 +177,9 @@ main_loop:
        ; draw lovebug
        mov di, (200 - 32) * 320 + 160 - 16
        mov ax, [num_frames]
+       shr ax, 2               ; /4
+       cmp ax, 200 - 32
+       jz .end
        mov bx, ax
        shl ax, 8
        shl bx, 6
@@ -190,11 +193,15 @@ main_loop:
        call blit32
 
 ; wait for vblank
-.vsync:
+.vsync_blank:
        mov dx, 3dah
        in al, dx
+       and al, 8
+       jnz     .vsync_blank
+.vsync_visible:
+       in al, dx
        and al, 8               ; the 4th bit is 1 when we are in the vertical blanking period
-       jnz     .vsync
+       jz .vsync_visible
 
 ; copy backbuffer to video memory
        push es
@@ -211,8 +218,9 @@ main_loop:
        pop es
 
        inc word [num_frames]
-       cmp word [num_frames], 200 - 32
-       jz .end
+;   moved above:
+;      cmp word [num_frames], 200 - 32
+;      jz .end
 
        in al, 64h              ; 60h = keyb data port, 64h = keyb status port
        and al, 1               ; 1 = OUTBUF_FULL = the keyb controller out buf is full