let a=0;
function setup() {
createCanvas(600, 600);
background(100);
}
function draw() {
a+=0.1;
push();
translate(mouseX,mouseY);
rotate(a);
scale(map(mouseX,0,600,0,1));
rect(100, 100, 100, 100);
}
<script src='https://cdn.jsdelivr.net/npm/p5@1.1.9/lib/p5.min.js'></script>