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)
noStroke()
global max_distance
max_distance = dist(0, 0, width, height)
def draw():
background(0)
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)
```