millfork/examples/c64/rasterbar.mfk

void main() {
    byte colour
    byte colour_index
    byte wait_for
    byte bar_start
    byte direction
    colour = 0
    disable_irq()
    vic_cr1 = 0
    vic_border = black
    bar_start = $50
    direction = 1
    while true {
        wait_for = bar_start
        for colour_index, 0, until, colours.length {
            colour = colours[colour_index]
            while wait_for != vic_raster  { }
            stabilize(10)
            vic_border = colour
            wait_for += 2
        }
        bar_start += direction
        if bar_start == $50 { direction = 1 }
        if bar_start == $A0 { direction = $ff }
    }

}

inline asm void stabilize(byte x){
    burn:
    DEX
    BNE burn
    ? RTS
}

const array colours = [
    $06, $06, $06, $0e, $06, $0e, 
    $0e, $06, $0e, $0e, $0e, $03, 
    $0e, $03, $03, $0e, $03, $03, 
    $03, $01, $03, $01, $01, $03, 
    $01, $01, $01, $03, $01, $01, 
    $03, $01, $03, $03, $03, $0e, 
    $03, $03, $0e, $03, $0e, $0e, 
    $0e, $06, $0e, $0e, $06, $0e, 
    $06, $06, $06, $00, $00, $00
]