Move the mouse across the image to obscure and reveal the matrix. Measures the distance from the mouse to each square and sets the size proportionally.

def setup():
    size(640, 360)
    global max_distance
    max_distance = dist(0, 0, width, height)

def draw():
    for i in range(0, width, 20):
        for j in range(0, height, 20):
            size = dist(mouseX, mouseY, i, j)
            size = size / max_distance * 66
            ellipse(i, j, size, size)