Few games have you "hello". Geometry wars is accessible, fun, and challenging.
There are 6 gameplay modes, and when you start up, you can see all your live friends high scores compared to your own. Each game starts up easy, and the difficulty cranks up from there. There is nothing easy about staying alive longer than 60 seconds in this game, and 3 of the game modes are 1 life and out. It is dynamic enough to pick up and play for 2 minutes, or sit and try to beat a high score in a marathon session.
The game is almost instantly addicting. I tried it with video game novices and pros alike, there is nothing quite like a fun and simple challenge that keeps the challenge going. You will not be upset that the 800 point download, I can guarantee it.