OpenLara is a clean-room engine reimplementation. It does not include any copyrighted game assets. You must legally own a copy of Tomb Raider (1996) to extract and use the required level and sound files.
If you manage to load OpenLara on a GBA or an emulator (like mGBA or Visual Boy Advance), here is what you can expect: openlara gba rom
Method A (For Flash Carts with FAT Support): OpenLara is a clean-room engine reimplementation
Method B (Creating a Single ROM):
The original Tomb Raider used a software-based polygon renderer. OpenLara on GBA uses a combination of fixed-point math and tile-based rendering. The GBA lacks a dedicated 3D GPU, so every polygon is drawn manually using the CPU. OpenLara cleverly reduces the draw distance, simplifies some geometry, and uses a lower color depth (15-bit color dithered to 8-bit where possible) to maintain a playable framerate of 15-20 FPS. Method B (Creating a Single ROM): The original