gistfile1.txt

// mouse events - mousePressed(), mouseReleased(), mouseMoved(), mouseDragged()
// runs once each time unlike mousepressed

var gray = 0;

function setup() {
    createGraphics(600, 400);
}

function draw() {
    background(gray);
}

function mousePressed() {
    gray += 20;
    console.log(gray)
}