Brent Silby created this game with one of his students and made it a learning experience for him. It's a pretty sweet game that starts out simple and easy but soon becomes harder and harder.

You (a turtle) start out bound to the earth with enemies coming at you. As you shoot your way through them, you pick up upgrades that give you two-directional fire and eventually the ability to fly. You'll need these as enemies start coming from above as well and before you know it they'll be everywhere - as seen in the second screenshot.

The game was made with DHTML and CSS sprites for animations. There is no sound.