dos33fsprogs/games/sb/hgr_logo_scroll.s
2023-06-01 14:29:59 -04:00

98 lines
1.5 KiB
ArmAsm

;================================
; HGR logo vscroll
;================================
; image to scroll in is in $4000
;
hgr_logo_vscroll:
ldx #191 ; 2
stx SCROLL ; SCROLL = 0 ; 3
vscroll_loop:
;====================
; draw bottom part
lda #0 ; 2
sta SCROLL_OFFSET ; offset in logo ; 3
ldx SCROLL ; offset in screen ; 3
vscroll_bottom:
cpx #192 ; 2
bcc regular_scroll ; 2/3
lda #$20
sta vscroll_in_smc+2
sta vscroll_out_smc+2
lda #$00
sta vscroll_in_smc+1
sta vscroll_out_smc+1
beq done_scroll_setup
regular_scroll:
ldy SCROLL_OFFSET ; 3
lda hposn_high,Y ; 4
eor #$60 ; $20->$40 ; 2
sta vscroll_in_smc+2 ; INH ; 4
lda hposn_low,Y ; 4
sta vscroll_in_smc+1 ; INL ; 4
;====
; 21
lda hposn_high,X ; 4
sta vscroll_out_smc+2 ; OUTH ; 4
lda hposn_low,X ; 4
sta vscroll_out_smc+1 ; OUTL ; 4
;====
; 21
done_scroll_setup:
inc SCROLL_OFFSET ; 5
ldy #39 ; 2
vscroll_bottom_line:
vscroll_in_smc:
lda $A000,Y ; 4
vscroll_out_smc:
sta $2000,Y ; 5
dey ; 2
bpl vscroll_bottom_line ; 2/3
;=====
; 2+40*(14)-1
; 561
inx ; 2
txa
sec
sbc SCROLL
cmp #58
bcc vscroll_bottom
;==========
;5+96*(42+561+7)-1
; 58564
done_scroll:
;=====================
; exit early if keypress
lda KEYPRESS
bmi vscroll_early_exit
;=====================
; scroll whole screen
dec SCROLL
bne vscroll_loop
vscroll_early_exit:
bit KEYRESET
rts