Cavernoi

In Cavernoi you control a flying robot exploring vast caverns of chunks of different materials. Your ship has tools that can manipulate parts of the cave around you to make your way through. Some materials can't be dug out or drilled and need to be avoided, or moved, and some will react with each other upon coming into contact.

There are solid, liquid, gaseous, hot, and radioactive materials, and tools to dig or drill, to remove a chunk as though it were never there, and to tug a chunk of material closer to you. Mouse controls movement (pathfinding with left button), tool selection (left-click a tool in the bottom bar), and tool use (right button on a chunk in range). Digging and drilling require being next to the chunk, while the others work at range. Dropping lava on yourself will harm your health, but nothing stops health going negative, so no need to be all that careful. Move off the right or bottom edges of the screen, by moving to them and then clicking close to the edge, to enter a new, more complex chamber each time.

This game was built using period tools (Borland Turbo C 3.0) and has reached a point where adding any single line of code causes it to crash immediately at run time, so it's stuck where it is. It crashes quite a bit anyway, but it's possible to play.