Play as a giant insect monster and try to protect the queen from an endless wave of determined attackers. Place other creatures around the path to help kill the enemies.
Eat enemies that are small enough to get bigger and stronger, or kill them to get resources used to buy and upgrade stuff or heal the queen.
I did go back to 2.49 to play it - it was pretty good. I liked the gameplay, and eating people was pretty funny. I liked how you could heal the queen, though I could only do it once (?). I didn’t even know it was a tower defense game until after I found out - it’s a pretty great job, man.