http://andyslife.org/games/game.php?file=magic-pen.swf

Your objective is to get a ball to one or more flags. You cannot directly manipulate it. Rather, you need to draw convex object with the mouse, each of which becomes a rigid body. You can use fixings and hinges too, but you rely entirely on gravity to provide the motion, which makes it pretty challenging, but a lot of fun.

It's a Flash game, and it's nice and slick (presumably unless you draw waaaaay to many objects!). Graphics are a nice kids' crayon kinda style, which makes it feel more fun. Well worth a try, as it's a nice casual challenge, albeit a tad infuriating at times!