toucans/emerald-rust

emerald-rust is a rebuild of the classic Game Boy Advance game Pokemon Emerald that lets you freely walk around its world, written in the Rust programming language. It is not trying to recreate the entire game with battles and story, it focuses on exploration: walking, running, riding a bike, and surfing through the whole Hoenn region, all 518 maps of it, at the same pace and feel as the original GBA game. It uses an existing fan project called pret/pokeemerald as its reference for how the original game's data and behavior actually work. The project runs both in a web browser, which is the main way to play it, and as a native program on your computer, from the same set of code. You can play it right now at the link in the README with no installation needed. Controls map to a game pad style layout on your keyboard, and touch controls appear automatically on phones. It includes music and sound effects recreated from the original game's sound engine, smooth zooming in and out, and a menu with a save-anywhere feature. A large part of the README is spent explaining a specific design decision the project cares about: the actual game logic, like movement and the camera, never talks directly to whatever graphics or audio library is being used underneath. Instead there is a small, narrow layer in between, so that if the graphics library the project depends on ever needs to be swapped out for something else in the future, only one small file has to change instead of the whole codebase. The author considers graphics libraries something that changes often over time, while the game itself is meant to last. To build it yourself, you need the Rust toolchain and its cargo build tool, plus a local copy of the pret/pokeemerald project to generate the world and music data files, since those are not included directly in the repository. A headless version that runs with no graphics at all is included as a way to test the game logic on its own. The README does not state what license the project is released under.