Seeing how everyone was posting one of these, I'll go with the flow.
How I got the idea
Initially I was pretty dissappointed with the theme, seeing how out of the 5 themes the only theme I couldn't really get an idea for was chosen. But I sat down for about an hour, chatted on IRC here and there, and suddenly got this neat idea.
What went right
During the development I think my best decision was to keep the game simple first, and once it was done and playable add more and more elements. This ensured I would have a game ready within the alloted timeframe and hopefully without too much bugs.
What went wrong
I spend too much time trying to make some sounds which I ended up deleting because they broke the rules. (Used drums and stuff which I distorted into explosion and gunshot sounds.) I could have much better spend this time on fixing some bugs.
For the future
Try and get more sleep before the competition, and no organizing any LAN parties afterwards. I was wasted. :D
I fixed a few bugs in the game after the LAN party, now, I know it wont count for the competition, but for anyone who would like a slightly more debugged version, http://deepflame.deeplyswitched.com/files/games/Tanks.zip should provide just what you're looking for. (It still contains various bugs, like, anything that manipulates it's window in any way will cause the game to freeze and/or crash.)
All in all, I had a really great time writing this game, and playing all the other games. There's some really neat stuff out there! :)