Apple II: Kaboom animation

kaboom.a

        *= $300;
        !cpu 65c02;
        
        ;Kaboom: Simple Lo-res color cycle just for fun
        
        php
        pha
        phx
        phy

	bit $c050
        bit $c052
        bit $c054
        
        ldx #$f
.outerLoop        
	;calculate byte value from color (0-F)
	lda colors,x
        asl
        asl
        asl
        asl
        adc colors,x
        
        ;fast-fill screen with color
        ldy #0
.loop
        sta $400,y
        sta $500,y
        sta $600,y
        sta $700,y
        iny
        bne .loop
        
        ;wait a little before advancing
        lda #$30
.pause1
        ldy #00
.pause2
	dey
        bne .pause2
        dec
        bne .pause1
    
        ;conclude animation
        dex
        bpl .outerLoop
        
        ;Reset screen
        jsr $FC58
        bit $c051
            
        ply
        plx
        pla
        plp
        rts

colors
        !byte %0000, %0001, %0010, %0100, %1000
        !byte %1100, %0110, %1010, %0011, %1001, %0101
        !byte %1110, %1011, %1101, %1110, %1111