Challenge: Falling leaves
Make leaves fall to the ground and pile up.

Add a falling leaf

Hint

mouseClicked = function() {
// add leaf here
};
draw = function() {
background(194, 231, 255);
tree.display();
// display leaf here
};

One common use of particle systems is to simulate falling leaves. We've drawn a tree in this program and
included a leaf-like Particle object in the code, and want you to make it so that clicking somewhere will
make a leaf fall from that point.