Oooo! First project on this account! This is a very simple 2d "ray caster", that solves for an intercept with the ground. Move your mouse around to move the lamp, and have fun!
This ray caster is not yet equipped to solve for intercepts other than the ground, so it will do the best it can to get the light to the ground. (This means there's a little weirdness with some things you can do.)