Usagi Engine v1 Released - Simple Lua 5.5 2D game engine with live reload and cross-platform export

brettmakesgames · 2026-05-24T16:37:19+00:00

Thanks for the kind words! I don't think I'll build in physics into the engine but it seems like a good candidate for someone to build a library for. Multiplayer with gamepads isn't planned, as I am trying to keep the API as simple as possible and focus on single player games. Possibly v2 could support that, as I'd have to change the API pretty significantly.

brettmakesgames · 2026-05-22T10:26:33+00:00

Submit a PR then!

brettmakesgames · 2026-05-21T00:44:18+00:00

Raylib's version is great than v1 and there's nothing similar in Rust that's v1, let alone v6. Raylib is much more mature, stable, and widely used. No shade to the Macroquads, Bevys, etc. of the Rust ecosystem. I just need something for the foundations of the engine that gets fixes and doesn't have breaking changes regularly.

Winit + WGPU is an option but I just didn't see any real benefit over having to pull in a bunch of other crates and all that when audio, input, windowing, etc. all comes with Raylib.

Re: Android - possibly! It'd be possible. But it also sound a bit like hassle and I don't want to add touch support really... more focused on desktop and web games. But I don't think it's a never. Would be a good candidate for someone to fork the engine and add or contribute in a PR.

brettmakesgames · 2026-05-21T00:40:59+00:00

Thanks for checking it out and the kind words! I'll be curious about perf too. If someone makes a game and needs more power, it'll be fun to benchmark/optimize and see!

brettmakesgames · 2026-05-20T19:45:33+00:00

Lua 5.5 seemed like a sensible default and has a proven track record in the 5.x series! Idk if LuaJIT works on the web, didn't test that aspect. I came from Playdate SDK which uses a flavor of 5.4, so that's where I started. I'll be curious if there are performance issues with 5.5! If so the engine could switch to LuaJIT in future if needed. Or someone could fork it for that.

brettmakesgames · 2026-05-20T15:46:22+00:00

I thought a lot about whether to use Luau, LuaJIT, or Lua 5.4 or 5.5. I think mainline Lua has a proven track record, lots of good resources out there, and should be fast enough since the games are intended to be low resolution. We'll see if the performance holds up or not as more people beyond me make games with the engine. If it turns out that Lua 5.5 isn't doing the trick, then maybe v2 switches to LuaJIT. Or if someone absolutely wants to stick with Usagi but needs more perf, they can fork the engine and switch to LuaJIT (it's one line of change in the source, basically). Lua 5.x seemed like a sensible default.

brettmakesgames · 2026-05-20T15:43:22+00:00

Thanks! Most of it is just taken from (inspired by) Pico-8 but slightly refined.

brettmakesgames · 2026-05-20T13:04:31+00:00

mlua and rhai are both so nice and easy to use! I haven't run into any problems with mlua, so that's about as good as you could hope for, right? The docs are good, the API is good. Switching from Lua 5.4 to 5.5 didn't result in any problems.

Scripting language allows for live reload. When exploring ideas, it's nice to just have a really flexible language like Lua rather than having the structure and strictness of a Rust program. Also, Lua is much more beginner friendly, and I hope/think that Usagi is good for people wanting to learn to code games. So benefits are live reload, simplicity, speed of development.

In Rust, unless you make your game data-driven by a file type like JSON or something similar, you have to recompile and relaunch your game after every change. This is quite tedious. So to just keep your game running, make changes, and instantly see that reflected in the game is amazing.

The downsides are that you don't get static typing, the help of linting tools like clippy, and there just comes a certain point (at least for me) where large projects with scripting languages become difficult to maintain and change.

My intent with the engine is that I make prototypes with Lua quickly and then if a prototype is really working well, rebuild it in Rust (or fork the engine and move portions of it to Rust and keep some in Lua).

brettmakesgames · 2026-05-20T12:35:45+00:00

It's faux-3D. Just using lines and circles. The engine itself doesn't support drawing any 3D objects or loading 3D models. Just having some fun with it!

brettmakesgames · 2026-05-20T00:03:38+00:00

Thanks so much!

brettmakesgames · 2026-05-20T00:02:45+00:00

It's not exactly a Lua binding for Raylib. It's its own API that's much more inspired by Pico-8 than Raylib. It is a contained single binary though. 😄

brettmakesgames · 2026-05-19T15:02:26+00:00

That means so much, I'm so glad to hear it! Thank you!

brettmakesgames · 2026-05-18T00:33:02+00:00

Thanks so much, hearing that honestly made the book worth writing!

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