First, if you don't know what line rider is, you have to check it out. This is the kind of fun little game that just breaks my wannabe game dev heart. So simple in appearance and execution. There's a fair amount going on under the hood of course, but it's incredibly easy to learn and play with. It's also hideously addictive. http://www.deviantart.com/deviation/40255643/
Now, if you had never seen that before, and managed to make it back to this page in less than 20 minutes... I'm impressed. At this point you're thinking, ok, I can quit any time I want.. and yeah it's neat, but so what? I will take this moment to show you what someone with way too much time and talent can pull off with the same simple tool... (and ultimately it is a tool, and a game, but I digress)
I give you this: http://www.youtube.com/watch?v=MFx-3UL42tA
Enjoy.
update: Even. Cooler. Still. http://www.youtube.com/watch?v=uFFQxW1LW58