Space Laser! is a physical alien shooting game in which you have 30 seconds to hit five aliens with your laser. If you successfully hit an alien's target, their lit eyes will dim and they will make a sad sound.
The game was built with 3 Arduinos, 3 batteries, 10 LEDs, 5 photocells, 5 servos, 1 laser diode, 1 speaker, and way too many wires. The code is available on Github. You can also find my in-progress documentation on my ITP blog.