# Sets the background gray value based on the distance 
# of the mouse from the center of the screen
def draw(): 
 noStroke()
 d = dist(width/2, height/2, mouseX, mouseY)
 maxDist = dist(0, 0, width/2, height/2)
 gray = map(d, 0, maxDist, 0, 255)
 fill(gray)
 rect(0, 0, width, height)