Ascension of the Drillworms is a really good game. It has cool, atmospheric music, and a graphical tiles presentation that reminds me of old ZX Spectrum games. It's written in C using the Allegro 5 game library.
You can find items, equipment and weapons.Part of the strategy involves which 4 gadgets you will choose to equip and which 4 "programs" you will run. There are things that will shield you, add to your damage, add to your accuracy and so on. Combat is ranged combat using your gun and your accuracy starts out bad so you miss a lot. The enemies shoot back at you. They start out as spidery crab things; later there are boss crabs that spawn smaller crabs; a new humanoid enemy appeared once I had cleared a few maps too.
To transition to the next map you simply find a cave entrance graphic and go in although sometimes you just stay there and don't go to the next map and have to come out, so I'm not sure if there's some task you have to perform on each level first or if some caves are just like that. Maybe they recover your stats.
You have three stats: armour, oxygen and energy. Armour is basically hp and can be fixed by spanners, Oxygen goes down with time and can be fixed with oxygen tanks. Energy is the weird one. Various devices you find use energy but I'm not sure if it's an ongoing cost or a "one time installation charge". All I can tell you is that before I worked out there was an inventory and character screen I had full energy, but then later, when I installed lots of stuff I never seemed to have any energy.
Anyway, it's a great game. I think two things would improve it though: one would be a couple of simple little sound effects for shooting and being hit and so on; the second thing would be a score of some kind or an indication of what level you were on.