AI War and its expansion, The Zenith Remnant, are both 50% off in celebration of a new "micro-expansion," Children of Neinzul. AI War is a grand strategy/4x/tower defense/rts and it's really fun if you're into that sort of thing (or maybe even if you aren't).
AI War pits up to 8 human commanders in a battle with 2 highly overpowered AI. This game is all about guerrilla warfare as you try to find the AI's home planets without causing such damage as to piss the AI off enough to rain hell upon your pathetic army until you forget what not being on fire felt like.
I'm not good at explaining things, so there's a demo that gives full access to the game only your campaigns can last at most 3 hours, and that's not really enough time to win even with only 10 planets (galaxy sizes range from 10 planets to 120) and the AI set to fail mode (difficulty goes from 1 ["sandbox"] to 10 ["Doom"]).
http://www.arcengames.com/ these people deserve your money. Also, Children of Neinzul proceeds all go to Child's Play. So, you know. Altruism and whatnot.
P.S. Arcen Games currently plan to keep updating this thing until 2013, and so far they've been doing a damn good job of it.
P.P.S. The current price is $10, $5, and $4 for base, expansion, and micro-expansion. It's usually $20, $10, and $4. And also if you don't buy it now a similar sale will probably happen in December when Expansion 2 ("Light of the Spire") comes out.
