Mark Wilcox has taken the gameplay from the classic Space Invaders arcade game, expanded a bit upon it and mixed it with his talent for making cool, cartoony B-movie inspired artwork. The result is Invaders from Mars.

My only complaint is that it's a bit sluggish (for me, at least). Everything seems to have been made with simple DOM elements and GIF files for the sprites. Sound effects have been made possible via SoundManager2.

Make sure you also visit Mark's blog where he talks about - among other things - the development of Invaders from Mars.