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| -rw-r--r-- | explosion.s.with_shaking | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/explosion.s.with_shaking b/explosion.s.with_shaking new file mode 100644 index 0000000..e5d297c --- /dev/null +++ b/explosion.s.with_shaking @@ -0,0 +1,96 @@ +; 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. + +; this version shakes the screen, but I'm not happy with how it +; looks. Might revisit at some point. + +; 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, tmp3, ptr1 + .import _jsleep + +color1save = tmp1 +color2save = tmp2 +shakectr = tmp3 +dlptr = ptr1 + +; 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 + + ; setup display list pointer (for screen shaking) + lda SDLSTL + sta dlptr + lda SDLSTL+1 + sta dlptr+1 + + ; dark text + lda #0 + sta COLOR1 + + ldy #2 ; loop counter, counts 2 1 0 + +; { +@loop: + lda color2save + ora #$0c ; embrighten text background (without changing the hue) + sta COLOR2 + + lda #2 + sta shakectr ; screen shaking counter + +; { +@shakeloop: + lda #$30 ; display list "blank 4 lines", replaces standard "blank 8 lines" + sta (dlptr),y + + ldx #0 ;\ + lda #$05 ; | jsleep(1)... _jsleep must NOT modify Y reg! + jsr _jsleep ;/ + + lda #$70 ; display list "blank 8 lines", put it back like it was + sta (dlptr),y + + ldx #0 ;\ + lda #$05 ; | jsleep(1); + jsr _jsleep ;/ + + dec shakectr + bne @shakeloop +; } + + lda color2save ; put text bg back like it was... + sta COLOR2 + + ldx #0 ; ...and jsleep(10) + lda #$0a + jsr _jsleep + + dey + bpl @loop ; we're done if Y < 0 +; } + + lda color1save ; restore text color + sta COLOR1 + rts +; } |