pong-more-or-less/main.asm

;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
	.include "c64.inc"
	.include "enum.asm"

	VMBASE		= $0400

	.org PROGSTART

	.include "init.asm"	;must come first
	.include "utilities.asm"

	;; Start screen, waits for space key to be pressed.
titlescreen:
	;; More visually interesting sprite positioning for
	;; the title screen. Overrides default from init.
	lda #$82
	sta SPRITE_0Y

	ldx #%01111111
	ldy #%00010000
	jsr keydown
	bne @dontstart
	;; Start the game here.
	jsr loadgamefield	;set the background
	lda #mode::MainGame	;don't forget that #
	sta gamemode		;set the game mode to MainGame
@dontstart:
	rts


	;; Wait and highlight the score change for half a second.
	;; Happens every time a player scores or whatever it's called in tennis
scorewait:
	;; While waiting we play a buzz
	lda #$0f
	sta SIDFMV
	lda #$08
	sta SIDAD1
	lda #$68
	sta SIDSR1

	lda #$45
	sta SIDF1L
	lda #$1d
	sta SIDF1H

	lda #$11
	sta SIDCR1

	dec timer
	bne @dontresume
	;; Reset gamemode
	lda #mode::MainGame
	sta gamemode
	;; Reset background color
	lda #0
	sta BGCOL0
	;; Stop sound
	lda #$10
	sta SIDCR1
@dontresume:
	rts


	;; Call after a player scores to highlight the win
highlightscore:
	lda #mode::ScoreHighlight
	sta gamemode
	lda #25
	sta timer
	lda #2
	sta BGCOL0
	rts

	.include "gameloop.asm"


	;; "Victory" mode when 100 points has been reached.
win:
	dec timer
	bne @skip
	dec timer2
	bne @continue
	;; After five seconds (10 half-seconds) we reset the game
	jmp PROGSTART
@continue:
	lda #25
	sta timer
	lda BGCOL0
	eor #8
	sta BGCOL0
@skip:
	rts

winstop:
	lda #25
	sta timer
	lda #10
	sta timer2
	lda #$0d
	sta BGCOL0
	lda #mode::Win		;DO NOT FORGET THE #
	sta gamemode
	rts

ball_x_inc:
	inc ball_x
	bne @done
	;; If ball_x incremented to zero we have either looped around
	;; the screen (shouldn't happen) or crossed the bit 8 boundry.
	;; So we set the MSB to one, since we're going right.
	lda #%00000100
	ora SPRITE_X_MSB
	sta SPRITE_X_MSB
@done:
	rts

ball_x_dec:
	dec ball_x
	lda ball_x
	cmp #$ff
	bne @done
	;; If ball_x incremented to zero we have either looped around
	;; the screen (shouldn't happen) or crossed the bit 8 boundry.
	;; So we set the MSB to one, since we're going right.
	lda #%11111011
	and SPRITE_X_MSB
	sta SPRITE_X_MSB
@done:
	rts

ball_bounce_vert:
	jsr color_change
	lda #%10000000
	eor balldata
	sta balldata
	rts

ball_bounce_hori:
	jsr color_change
	lda #%01000000
	eor balldata
	sta balldata
	rts

reset_ball:
	jsr ball_bounce_hori
	lda #$90
	sta ball_y
	lda #$c0
	sta ball_x
	lda #%11111011
	and SPRITE_X_MSB
	sta SPRITE_X_MSB
	rts

color_change:
	inc bordercol
	lda bordercol
	and #$0f
	cmp #2
	bcs @fine
	lda #2
	sta bordercol
@fine:
	lda bordercol
	sta BORDER
	rts

handle_collision:
	jsr ball_bounce_hori	;obvious, flip the ball's horizontal direction
	lda #$00
	sta col			;clear the collision flag
	rts

	;; Cheap trick to make a hexprinted number look decimal.
	;; Score comes in the A register, clamped score returned in A
clampscore:
	tax
	and #%00001111
	cmp #$0a
	bcc @noclamplower
	;; yes clamp, inc upper nybble, ex. $19 -> $20
	txa
	and #%11110000
	clc
	adc #$10
	tax
@noclamplower:
	txa
	and #%11110000
	cmp #$a0
	bcc @noclamp
	;; over 99? just stop at that point, we'll flash some colors then reset
	jsr winstop
	pla
	pla
@noclamp:
	txa
	rts

modedispatch:
	jsr jumpwithtable
	.addr titlescreen
	.addr game		;normal gameplay
	.addr scorewait
	.addr win


	;; Main IRQ subroutine. CPU gets sent here by the interrupts from the
	;; VIC-II's raster and collision interrupts, and is responsible for
	;; calling everything else. Since the game is interrupt-driven, you
	;; could add a RTS to the init code and have the game run together
	;; with BASIC. Would be pretty stupid but you *can* do it. That does
	;; give me an idea though...
irq:
	lda SSCOL		;need to do this for collision checking to work

	lda #%00000100		;check if irq is for collision or not
	and VICINT
	beq @nocol
	;; Collision
	sta col			;set the collision flag
	lda #$7f
	and VICINT
	sta VICINT
	jmp @skipgame
@nocol:
	lda gamemode
	jsr modedispatch
@skipgame:
	lda #$7f
	and VICINT
	sta VICINT

	jmp $ea31

	.include "variables.asm"

	BALLVERT	= %10000000
	BALLHORI	= %01000000
	BALLVSPEED	= %00000010
	BALLHSPEED	= %00000001

	.include "graphics.asm"
	.include "zeropage.asm"