Earlier I found an old game called Core Wars. Currently, the main homepage seems to be at
http://corewar.co.uk/. Amazingly, even after all this time it still has a slightly alive community.
Core Wars a game where you write a program in a sort of assembly code and design it for war against other such programs. Programs are called Warriors, and they're placed in a circular area of memory called the core. The core wraps around, which makes it appear to the programs running inside it as infinite. Multiple programs are placed in the core at a time, and they execute until there's only one left.
There are multiple strategies for winning. You can search for other programs then try to destroy them, you can try to stun them, you can try to blindly attack, or you can replicate yourself until you're almost impossible to kill.
While programming isn't very hard to pick up, I wouldn't recommend this game to people who don't already have some experience in the subject, and knowing assembly would probably help, although working in core wars requires you to think a little differently than you would when making a regular program.
There are still many hill servers up where you can test your own warriors against others, and try to get on the high score list. If you get into this, you'll definitely want to read some old newsletters and articles on strategy that can be found with a few searches.
While I haven't made any high score lists myself (except for a short-lived 25th place on the beginner hill), I still enjoyed making basic warriors and pitting them against each other on my own computer using a simulator (I recommend CoreWin).
So with that wall of text over with, what do you think about Core Wars? Do you think you're going to give it a try? If you have, feel free to ask any questions you have below, or to post any warriors you're working on or have completed. I'd post a few of my own warriors but they were lost in a tragic accident where I had to reinstall windows.