Processingのおさらい（第6問）

r = 0
isReversed = False

def setup():
    size(600, 600)
    noStroke()
    
def draw():
    background(0)
    global r, isReversed
    if isReversed:
        r -= 1
    else:
        r += 1

    if r < 0:
        isReversed = False
    elif r > 255:
        isReversed = True

    for y in range(10):
        for x in range(10):
            fill(r, x * 25, y * 25)
            rect(x * 60, y * 60, 60, 60)