315 lines
6.4 KiB
NASM
315 lines
6.4 KiB
NASM
; -----------------------------------------------------------
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; credits.asm - demo style credits: a smooth pixel scroller
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; along the top (slide1's fine-scroll trick), gold wash on the
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; big CREDITS, pulsing TELETYPE GAMES, rainbow crew names and
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; a sprite parade of the scooter chasing the rabbits
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; -----------------------------------------------------------
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CR_SCROW = 1 ; scroller char row (raster lines 58-65)
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CR_RASTOP = 56 ; switch fine scroll on just above it
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CR_RASBOT = 66 ; ... and off just below (rows 0/2 are blank)
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CR_STEP = 2 ; scroll speed: 8 px / 4 frames = 1 char
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CR_PARADE_Y = 228 ; the parade runs along the bottom rows
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credits_init:
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lda #BLACK ; same black card style as the menu
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sta bg_top
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sta bg_bot
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jsr clear_screen
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+prbig 4, 6, YELLOW, txt_credits, 7
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+prtext 11, 13, WHITE, txt_ttgname, 14
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+prtext 13, 8, LGREEN, txt_crew0, 23
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+prtext 14, 10, LGREEN, txt_crew1, 20
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+prtext 15, 9, LGREEN, txt_crew2, 21
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+prtext 16, 10, LGREEN, txt_crew3, 20
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+prtext 18, 9, LGREY, txt_ai1, 22
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+prtext 19, 12, LGREY, txt_ai2, 16
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; the scroller row renders in white
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ldx #39
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ci_scol:
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lda #WHITE
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sta COLRAM+CR_SCROW*40,x
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dex
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bpl ci_scol
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lda #6 ; multiple of CR_STEP -> clean 4-frame cycle
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sta xscroll
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lda #0
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sta scrollidx
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sta washphase
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; parade sprites: the red scooter chases seven white rabbits
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lda #RED
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sta SPR_COL
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ldx #7
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ci_col:
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lda #WHITE
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sta SPR_COL,x
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dex
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bne ci_col
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lda #SPRP_SCOOT
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sta SPRPTR
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lda #0
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sta SPR_XEX
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sta SPR_YEX
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lda #$ff
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sta SPR_EN
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+setupd credits_update
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rts
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credits_update:
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; ---- all the heavy drawing runs first, while the beam
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; is still far above the scroller row ----
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; scroller: step the fine scroll, shift on wrap-around
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lda xscroll
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sec
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sbc #CR_STEP
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bpl cu_noshift
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clc
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adc #8
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sta xscroll
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ldx #0
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cu_shift:
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lda SCREEN+CR_SCROW*40+1,x
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sta SCREEN+CR_SCROW*40,x
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inx
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cpx #39
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bne cu_shift
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ldx scrollidx ; feed the next char in on the right
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lda scrolltext,x
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sta SCREEN+CR_SCROW*40+39
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inx
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cpx #scrolltext_end - scrolltext
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bne cu_feedok
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ldx #0
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cu_feedok:
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stx scrollidx
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jmp cu_scrolled
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cu_noshift:
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sta xscroll
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cu_scrolled:
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; gold wash rolling down the big CREDITS (rows 4-8; the
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; letters are inverse spaces, color RAM on blanks is moot)
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inc washphase
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lda #0
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sta g8row
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cu_wash:
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lda #4
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clc
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adc g8row
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tax
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jsr row_ptr
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lda washphase
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lsr
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clc
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adc g8row
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and #15
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tax
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lda washtbl,x
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ldy #33
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cu_wcol:
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sta (collo),y
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dey
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cpy #5
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bne cu_wcol
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inc g8row
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lda g8row
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cmp #5
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bne cu_wash
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; TELETYPE GAMES pulses grey-white
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ldx #11
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jsr row_ptr
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lda framectr
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lsr
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lsr
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lsr
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and #7
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tax
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lda pulsetbl,x
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ldy #26
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cu_pulse:
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sta (collo),y
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dey
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cpy #12
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bne cu_pulse
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; rainbow runs down the crew lines
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lda #0
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sta rtmp2 ; line counter
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cu_crew:
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lda #13
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clc
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adc rtmp2
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tax
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jsr row_ptr
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lda framectr
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lsr
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lsr
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clc
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adc rtmp2
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and #7
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tax
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lda raintbl,x
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ldy #31
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cu_ccol:
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sta (collo),y
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dey
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cpy #7
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bne cu_ccol
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inc rtmp2
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lda rtmp2
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cmp #4
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bne cu_crew
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; the parade: everything scoots right to left, wraps at 344
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ldx #7
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cu_par:
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lda crx_lo,x
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sec
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sbc crspd,x
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sta crx_lo,x
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lda crx_hi,x
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sbc #0
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sta crx_hi,x
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bne cu_ponscr ; x >= 256: still on screen
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lda crx_lo,x
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cmp #24
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bcs cu_ponscr
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lda #$58 ; wrapped: back to x = 344
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sta crx_lo,x
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lda #1
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sta crx_hi,x
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cu_ponscr:
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txa
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asl
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tay
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lda crx_lo,x
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sta SPRPOS,y
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cpx #0
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beq cu_pscoot
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; rabbits bob and cycle their hop frames
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lda framectr
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lsr
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lsr
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lsr
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sta rtmp
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txa
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clc
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adc rtmp
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and #7
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tay
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lda hoptab,y
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sta rtmp
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lda #CR_PARADE_Y
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sec
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sbc rtmp
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pha
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lda framectr
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lsr
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lsr
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lsr
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sta rtmp
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txa
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clc
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adc rtmp
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and #3
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clc
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adc #SPRP_BIG
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sta SPRPTR,x
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txa
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asl
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tay
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pla
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sta SPRPOS+1,y
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jmp cu_pnext
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cu_pscoot:
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lda #CR_PARADE_Y
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sta SPRPOS+1
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cu_pnext:
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dex
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bpl cu_par
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; x MSB shadow from the high bytes
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lda #0
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sta rtmp
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ldx #7
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cu_pmsb:
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lda crx_hi,x
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beq cu_pmnext
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lda crbit,x
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ora rtmp
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sta rtmp
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cu_pmnext:
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dex
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bpl cu_pmsb
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lda rtmp
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sta SPR_MSBX
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; blink the return prompt
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lda framectr
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and #32
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bne cu_hide
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+prtext 21, 13, YELLOW, txt_return, 13
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jmp cu_input
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cu_hide:
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+prtext 21, 13, YELLOW, txt_blank, 13
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cu_input:
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jsr start_edge
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beq cu_stay
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lda #$c8 ; leave with the scroll register clean
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sta XCTRL
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jmp menu_init ; back to the menu
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cu_stay:
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; ---- beam work: fine scroll on for the scroller row only ----
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cu_wtop:
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lda RASTER
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cmp #CR_RASTOP
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bne cu_wtop
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lda xscroll ; bits 0-2 = x scroll, bit 3 = 0 -> 38 cols
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sta XCTRL
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cu_wbot:
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lda RASTER
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cmp #CR_RASBOT
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bne cu_wbot
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lda #$c8 ; back to default: 40 columns, no scroll
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sta XCTRL
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rts
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; ---- tables ----
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pulsetbl: ; grey-white pulse (8 entries, cyclic)
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!byte $0b, $0c, $0f, $01, $01, $0f, $0c, $0b
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raintbl: ; rainbow ramp for the crew lines
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!byte $02, $08, $07, $0d, $03, $0e, $04, $0a
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crbit: ; sprite number -> register bit
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!byte 1, 2, 4, 8, 16, 32, 64, 128
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crspd: ; parade speeds (sprite 0 = the scooter)
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!byte 2, 1, 3, 1, 2, 1, 3, 2
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crx_lo: ; parade x positions (16 bit, start staggered)
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!byte 60, 100, 140, 180, 220, 4, 44, 84
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crx_hi:
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!byte 0, 0, 0, 0, 0, 1, 1, 1
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; ---- scrolltext (wraps around) ----
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scrolltext:
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!scr "welcome to rabbit scooter ... the crew: "
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!scr "mr.zero - tasnadi zsolt ... mr.one - tari balazs ... "
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!scr "mr.two - timar zoltan ... mr.three - mezo bela ... "
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!scr "this whole game was written by an ai - honest! ... "
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!scr "greetings to all sceners out there ... "
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scrolltext_end:
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; ---- credits variables ----
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xscroll: !byte 6 ; fine scroll register value (0-7)
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scrollidx: !byte 0 ; next scrolltext char to feed in
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