rewrote screen-flash in asm, save a few bytes

1 files changed, 66 insertions, 0 deletions

diff --git a/explosion.s b/explosion.s
new file mode 100644
index 0000000..581e987
--- /dev/null
+++ b/explosion.s
@@ -0,0 +1,66 @@
+; explosion seen when we're hit by enemy fire.
+; currently just flashes the screen. the apple version is
+; kinda funky-looking, best way I can describe it is that it
+; looks like TV static. would be hard to imitate that on the
+; atari. maybe there should be screen-shaking going on?
+
+; original code was in C, and looked like:
+;; for(i = 0; i < 3; i++) {
+;; 	unsigned char color = PEEK(710) & 0xf0;
+;; 	unsigned char textcolor = PEEK(709);
+;; 	POKE(709,0);
+;; 	POKE(710, color | 0x0c);
+;; 	jsleep(10);
+;; 	POKE(710, color & 0xf0);
+;; 	jsleep(10);
+;; 	POKE(709,textcolor);
+;; }
+
+ .export _explosion
+ .include "atari.inc"
+ .importzp tmp1, tmp2
+ .import _jsleep
+
+color1save = tmp1
+color2save = tmp2
+
+; extern void explosion(void);
+_explosion:
+; {
+ ; save original colors (don't hardcode, they can be changed on the title screen)
+ lda COLOR1
+ sta color1save
+ lda COLOR2
+ sta color2save
+
+ ; dark text
+ lda #0
+ sta COLOR1
+
+ ldy #3 ; loop counter, counts 3 2 1
+
+;   {
+@loop:
+ lda color2save
+ ora #$0c   ; embrighten text background (without changing the hue)
+ sta COLOR2
+
+ ldx #0      ;\
+ lda #$0a    ; | jsleep(10);
+ jsr _jsleep ;/
+
+ lda color2save ; put text bg back like it was...
+ sta COLOR2
+
+ ldx #0         ; ...and jsleep(10) again
+ lda #$0a
+ jsr _jsleep
+
+ dey
+ bne @loop ; we're done if Y==0
+;   }
+
+ lda color1save ; restore text color
+ sta COLOR1
+ rts
+; }