Challenge: Magical cauldron
Emit stars and smoke from the cauldron.

Add smoke!

Hint

var Smoke = function() {
;
};
Smoke.prototype = Object.create();
Smoke.prototype.display = function() {
// make it look like smoke!
};

This program animates a standard particle system emerging out of a cauldron. We want different sorts of
particles to come out of the cauldron, though, starting with a smoky particle. Create a Smoke object that
inherits from Particle, but looks more like coloured smoke.