initial commit

play.asm

@@ -0,0 +1,291 @@
+; -----------------------------------------------------------
+; play.asm - the game: lane movement with key-repeat, rabbit
+; spawning with a score-driven interval, arrivals scored or
+; counted as a miss, HUD updates
+; -----------------------------------------------------------
+
+; ---- start (or restart) a round ----
+play_init:
+    jsr clear_screen
+    jsr draw_road
+
+    ; HUD: score on the left, miss slots on the right
+    +prtext 0, 1, BLACK, txt_score, 5
+    +prtext 0, 30, BLACK, txt_miss, 4
+
+    lda #0
+    sta score8
+    sta sc_d0
+    sta sc_d1
+    sta sc_d2
+    sta miss
+    sta flash
+    sta spawnt
+    sta lcnt
+    sta rcnt
+    jsr draw_score
+
+    lda #0               ; draw_score leaves a digit code in A
+    ldx #NRABBITS-1
+pi_clr:
+    sta r_act,x
+    dex
+    bpl pi_clr
+
+    lda #2               ; start in the middle lane
+    sta player_lane
+
+    ; player sprite: scooter, fixed row, rabbits come per frame
+    lda #SPRP_SCOOT
+    sta SPRPTR
+    lda #PLAYER_SY
+    sta SPRPOS+1
+    lda #1
+    sta SPR_EN
+    lda #0
+    sta SPR_XEX
+    sta SPR_YEX
+
+    +setupd play_update
+    rts
+
+; ---- one frame of gameplay ----
+play_update:
+    jsr read_joy
+
+    ; -- left: move on press, then auto-repeat while held --
+    lda joyb
+    and #JOY_LEFT
+    beq pu_lrel
+    inc lcnt
+    lda lcnt
+    cmp #1
+    beq pu_lmove
+    cmp #REP_HOLD+REP_PERIOD
+    bne pu_lend
+    lda #REP_HOLD
+    sta lcnt
+pu_lmove:
+    lda player_lane
+    beq pu_lend
+    dec player_lane
+    jmp pu_lend
+pu_lrel:
+    lda #0
+    sta lcnt
+pu_lend:
+
+    ; -- right, same dance --
+    lda joyb
+    and #JOY_RIGHT
+    beq pu_rrel
+    inc rcnt
+    lda rcnt
+    cmp #1
+    beq pu_rmove
+    cmp #REP_HOLD+REP_PERIOD
+    bne pu_rend
+    lda #REP_HOLD
+    sta rcnt
+pu_rmove:
+    lda player_lane
+    cmp #LANES-1
+    beq pu_rend
+    inc player_lane
+    jmp pu_rend
+pu_rrel:
+    lda #0
+    sta rcnt
+pu_rend:
+
+    ; -- shadow init: player sprite bit + its x MSB --
+    ldx player_lane
+    lda pxlo,x
+    sta SPRPOS           ; sprite 0 x
+    lda pxhi,x
+    sta msb_sh           ; lane 4 sits past x=255
+    lda #0
+    sta xex_sh
+    sta yex_sh
+    lda #1
+    sta en_sh
+
+    ; -- a hit blinks the scooter for a dozen frames --
+    lda flash
+    beq pu_noflash
+    dec flash
+    lda framectr
+    and #4
+    bne pu_noflash
+    lda #0
+    sta en_sh
+pu_noflash:
+
+    ; -- spawn: interval = 70 - score/2, floor 22 (as the original) --
+    inc spawnt
+    lda score8
+    cmp #96
+    bcc pu_ivcalc
+    lda #22
+    jmp pu_ivgot
+pu_ivcalc:
+    lsr
+    sta rtmp
+    lda #70
+    sec
+    sbc rtmp
+pu_ivgot:
+    cmp spawnt
+    bcs pu_nospawn
+    lda #0
+    sta spawnt
+    jsr spawn_rabbit
+pu_nospawn:
+
+    ; -- advance every live rabbit --
+    ldx #NRABBITS-1
+pu_rab:
+    lda r_act,x
+    beq pu_rnext
+    lda r_tlo,x          ; t += speed (8.8 fixed point)
+    clc
+    adc r_splo,x
+    sta r_tlo,x
+    lda r_thi,x
+    adc r_sphi,x
+    sta r_thi,x
+    bcc pu_ralive
+    ; arrived at the player line
+    lda #0
+    sta r_act,x
+    lda r_lane,x
+    cmp player_lane
+    beq pu_rhit
+    jsr add_score        ; dodged: one point
+    jmp pu_rnext
+pu_rhit:
+    jsr add_miss         ; ran into you
+    jmp pu_rnext
+pu_ralive:
+    jsr rab_pos
+pu_rnext:
+    dex
+    bpl pu_rab
+
+    jsr write_shadows
+
+    ; -- third miss ends the round --
+    lda miss
+    cmp #MAX_MISS
+    bcc pu_done
+    jmp over_init        ; its rts returns to the main loop
+pu_done:
+    rts
+
+; ---- claim a free rabbit slot and roll its lane + speed ----
+spawn_rabbit:
+    ldx #NRABBITS-1
+sr_find:
+    lda r_act,x
+    beq sr_got
+    dex
+    bpl sr_find
+    rts                  ; every slot busy: skip this spawn
+sr_got:
+    lda #1
+    sta r_act,x
+    jsr rand5
+    sta r_lane,x
+    lda #0
+    sta r_tlo,x
+    sta r_thi,x
+    ; speed = $0260 base + random byte + score ramp (tops out at 64)
+    jsr rand8
+    clc
+    adc #$60
+    sta rtmp
+    lda #2
+    adc #0
+    sta rtmp2
+    lda score8
+    cmp #64
+    bcc sr_ramp
+    lda #64
+sr_ramp:
+    tay
+    lda rtmp
+    clc
+    adc sptab_lo,y
+    sta r_splo,x
+    lda rtmp2
+    adc sptab_hi,y
+    sta r_sphi,x
+    rts
+
+; ---- score: bump the decimal digits and the difficulty byte ----
+add_score:
+    lda score8
+    cmp #$ff
+    beq as_digits
+    inc score8
+as_digits:
+    inc sc_d2
+    lda sc_d2
+    cmp #10
+    bne draw_score
+    lda #0
+    sta sc_d2
+    inc sc_d1
+    lda sc_d1
+    cmp #10
+    bne draw_score
+    lda #0
+    sta sc_d1
+    inc sc_d0
+    lda sc_d0
+    cmp #10
+    bne draw_score
+    lda #0
+    sta sc_d0
+; falls through: repaint the three HUD digits
+draw_score:
+    lda sc_d0
+    ora #48              ; digit screen codes start at 48
+    sta SCREEN+7
+    lda sc_d1
+    ora #48
+    sta SCREEN+8
+    lda sc_d2
+    ora #48
+    sta SCREEN+9
+    rts
+
+; ---- miss: X mark on the HUD + blink the scooter ----
+add_miss:
+    inc miss
+    ldy miss             ; Y: the rabbit loop still needs X
+    lda #24              ; 'x'
+    sta SCREEN+34,y      ; marks land on columns 35-37
+    lda #12
+    sta flash
+    rts
+
+; ---- gameplay variables ----
+player_lane: !byte 2
+score8:      !byte 0     ; score capped at 255, drives the difficulty
+sc_d0:       !byte 0     ; score digits: hundreds, tens, ones
+sc_d1:       !byte 0
+sc_d2:       !byte 0
+miss:        !byte 0
+flash:       !byte 0     ; frames left of the post-hit blink
+spawnt:      !byte 0     ; frames since the last spawn
+lcnt:        !byte 0     ; held-direction counters for the auto-repeat
+rcnt:        !byte 0
+
+; ---- rabbit slots (hardware sprites 1-7) ----
+r_act:  !fill NRABBITS, 0
+r_lane: !fill NRABBITS, 0
+r_tlo:  !fill NRABBITS, 0    ; distance along the lane, 8.8 fixed point
+r_thi:  !fill NRABBITS, 0
+r_splo: !fill NRABBITS, 0    ; per-rabbit speed, 8.8 fixed point
+r_sphi: !fill NRABBITS, 0