The tomb4 project by Troye is a decompilation project that, first and foremost aims to document and preserve the original source code and assets of the game, and secondly, aims to provide bug fixes and gameplay improvements in many sections of the game.
The project is fully open source, and the code can be used anywhere under the aforementioned license in the repository, along with credit.
Fixes:
Check out the changelog for the full list of fixes and additions! Highlights include: PSX Bars, fixed bugs, properly scaled effects, and much more!
Some screenshots:
How to install:
Troye created a useful using guide to help you installing it.
