This is an old game I made back in 2004 (with minor edits in later years) using my friend's 3D step-based engine: The Dantares Engine by Ryan Witmer. You can find the original code in relics/.
I originally made it for Windows only. In 2024, I re-wrote the code for it in SDL (tested on Linux) using modern C++20. However, it still uses The Dantares Engine and requires legacy OpenGL 2.0+.
The code is a bit over-engineered, but I designed it so that I could use parts of it in other projects. I was planning to make a simple ECS, but because the game is quite simple and the ECS code produced more files/lines of code, I decided to just to stick with the original class-based structure.