Magic-Pen is a beautiful physics-based puzzle playground. Using the mouse, you must draw shapes to create bridges and swings, guiding the red ball to the flag. Making shapes and dropping them from the sky will set the ball in motion, you can also craft structures with hinges (both fixed and movable) for more complex maneuvers. The shapes you draw are affected by three basic principles: gravity, friction, and inertia. In other words, common sense physics.
Magic-Pen is one of my favorite online timewasters. It took me several hours to complete, and I enjoyed every minute. I hope you're as impressed with it as I was.