112 lines
3.0 KiB
NASM
112 lines
3.0 KiB
NASM
; -----------------------------------------------------------
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; main.asm - RABBIT SCOOTER for the C64
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; port of the rabbitroller Game & Watch style LCD game:
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; rabbits hop toward you on a five-lane road, dodge them
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; on your scooter - a rabbit reaching your lane is a miss,
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; one passing in another lane is a point; 3 misses = over
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;
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; Files:
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; defs.asm - constants, zero page, macros
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; title.asm - title screen: demo rabbits + press fire
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; play.asm - the game itself
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; over.asm - game over box + retry
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; common.asm - shared routines, input, rabbit positioning
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; tables.asm - perspective / speed tables (assembly-time)
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; sprites.asm - sprite art (scooter, small + big rabbits)
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;
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; Build: acme -f cbm -o rabbit.prg main.asm
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; -----------------------------------------------------------
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!to "rabbit.prg", cbm
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* = $0801
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; ---- BASIC stub: 10 SYS 2064 ----
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; so after LOAD"*",8,1 it's enough to type RUN
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!byte $0c, $08 ; address of next line
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!byte $0a, $00 ; line number: 10
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!byte $9e ; SYS token
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!byte $20, $32, $30, $36, $34 ; " 2064"
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!byte $00 ; end of line
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!byte $00, $00 ; end of program
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* = $0810 ; = 2064 in decimal
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!src "defs.asm"
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start:
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sei ; no KERNAL IRQ - raster polling must not jitter
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; LCD look: black bezel border, pale screen, black artwork
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lda #BLACK
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sta BORDER
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lda #LGREY
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sta BG
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; sprites: all black, hires, in front of the characters
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ldx #7
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sprcol:
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lda #BLACK
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sta SPR_COL,x
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dex
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bpl sprcol
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lda #0
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sta SPR_EN
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sta SPR_MC
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sta SPR_PRIO
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sta SPR_MSBX
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sta SPR_XEX
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sta SPR_YEX
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sta framectr
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sta fheld
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!ifdef AUTOPLAY { ; test builds boot straight into the game
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jsr play_init
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} else {
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jsr title_init
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}
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; ============================================================
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; main loop - one state update per PAL frame, synced to the
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; raster beam in the lower border
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; ============================================================
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main:
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jsr wait_frame
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inc framectr
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jsr rand8 ; stir the RNG once per frame
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jsr call_update
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jmp main
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call_update:
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jmp (updvec) ; each update runs exactly one frame, ends with rts
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; ---- wait for raster line RAS_SYNC (leave it first, so a
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; fast update cannot run twice in the same frame) ----
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wait_frame:
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lda RASTER
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cmp #RAS_SYNC
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beq wait_frame
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wf_hit:
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lda RASTER
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cmp #RAS_SYNC
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bne wf_hit
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rts
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; ============================================================
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; sprite art first: it must stay below $1000, where the VIC
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; would see the character ROM shadow instead of our RAM
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; ============================================================
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!src "sprites.asm"
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!if * > $1000 {
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!error "sprite data ran into the char ROM shadow at $1000"
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}
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; ============================================================
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; the states and everything they share
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; ============================================================
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!src "title.asm"
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!src "play.asm"
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!src "over.asm"
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!src "common.asm"
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!src "tables.asm"
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