Quite a while ago, there was a game on here that was about a guy stuck in a pit with a talking, sentient gun. You would climb upwards through the levels, collecting gems (traded for upgrades), shooting enemies, and there was a boss at the end of each level.
There was also a crazy evil scientist.
I have spent a long time looking through the games, trying to find this one again. If anyone remembers the name, please share!
