let a=0;
function setup() {
createCanvas(600, 600);
background(100);
}
function draw() {
a+=0.2;
push();
translate(mouseX,mouseY);
rotate(a);
scale(map(mouseX,0,500,0,2));
rect(100, 0, 100, 100);
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.1.9/p5.min.js"></script>