Odin + Raylib + Hot Reload template

This is an Odin + Raylib game template with Hot Reloading pre-setup. It makes it possible to reload gameplay code while the game is running.

Supported platforms: Windows, macOS, Linux and web.

Supported editors and debuggers: Sublime Text, VS Code and RAD Debugger.

See The Legend of Tuna repository for an example project that also uses Box2D: https://github.com/karl-zylinski/the-legend-of-tuna

I used this kind of hot reloading while developing my game CAT & ONION.

Hot reload quick start

Note

These instructions use some Windows terminology. If you are on mac / linux, then replace these words:

• bat -> sh
• exe -> bin
• dll -> dylib (mac), so (linux)

1. Run build_hot_reload.bat to create game_hot_reload.exe and game.dll (located in build/hot_reload). Note: It expects odin compiler to be part of your PATH environment variable.
2. Run game_hot_reload.exe, leave it running.
3. Make changes to the gameplay code in source/game.odin. For example, change the line rl.ClearBackground(rl.BLACK) so that it instead uses rl.BLUE. Save the file.
4. Run build_hot_reload.bat, it will recompile game.dll.
5. The running game_hot_reload.exe will see that game.dll changed and reload it. But it will use the same Game_Memory (a struct defined in source/game.odin) as before. This will make the game use your new code without having to restart.

Note, in step 4: build_hot_reload.bat does not rebuild game_hot_reload.exe. It checks if game_hot_reload.exe is already running. If it is, then it skips compiling it.

Release builds

Run build_release.bat to create a release build in build/release. That exe does not have the hot reloading stuff, since you probably do not want that in the released version of your game. This means that the release version does not use game.dll, instead it imports the source folder as a normal Odin package.

build_debug.bat is like build_release.bat but makes a debuggable executable, in case you need to debug your non-hot-reload-exe.

Web build

build_web.bat builds a release web executable (no hot reloading!).

Web build requirements

• Emscripten. Download and install somewhere on your computer. Follow the instructions here: https://emscripten.org/docs/getting_started/downloads.html (follow the stuff under "Installation instructions using the emsdk (recommended)").
• Recent Odin compiler: This uses Raylib binding changes that were done on January 1, 2025.

Web build quick start

1. Point EMSCRIPTEN_SDK_DIR in build_web.bat/sh to where you installed emscripten.
2. Run build_web.bat/sh.
3. Web game is in the build/web folder.

Note

build_web.bat is for windows, build_web.sh is for Linux / macOS.

Warning

You can't run build/web/index.html directly due to "CORS policy" javascript errors. You can work around that by running a small python web server:

• Go to build/web in a console.
• Run python -m http.server
• Go to localhost:8000 in your browser.

For those who don't have python: Emscripten comes with it. See the python folder in your emscripten installation directory.

Build a desktop executable using build_desktop.bat/sh. It will end up in the build/desktop folder.

There's a wrapper for read_entire_file and write_entire_file from core:os that can files from assets directory, even on web. See source/utils.odin

Assets

You can put assets such as textures, sounds and music in the assets folder. That folder will be copied when a release build is created and also integrated into the web build.

The hot reload build doesn't do any copying, because the hot reload executable lives in the root of the repository, alongside the assets folder.

Sublime Text

For those who use Sublime Text there's a project file: project.sublime-project.

How to use:

• Open the project file in sublime
• Choose the build system Main Menu -> Tools -> Build System -> Odin + Raylib + Hot Reload template (you can rename the build system by editing project.sublime-project manually)
• Compile and run by pressing using F7 / Ctrl + B / Cmd + B
• After you make code changes and want to hot reload, just hit F7 / Ctrl + B / Cmd + B again

RAD Debugger

You can hot reload while attached to RAD Debugger. Attach to your game_hot_reload executable, make code changes in your code editor and re-run the the build_hot_reload script to build and hot reload.

VS Code

You can build, debug and hot reload from within VS Code. Open the template using File -> Open Folder....

Requirements for debugging to work:

• Windows: C++ build tools
• Linux / Mac: CodeLLDB

Launch with Run Hot Reload launch task, see image above. After you make code changes press Ctrl + Shift + B to rebuild and hot reload.

Windows Debugging hacks

On Windows the degugging while hot reloading works by outputting a new PDB each time the game DLL is built. It cleans up the PDBs when you do a fresh start. See build_hot_reload.bat for details.

Demo streams

Streams that start from this template:

• 48 hour "Odin Holiday Gamejam": https://www.youtube.com/playlist?list=PLxE7SoPYTef2XC-ObA811vIefj02uSGnB Every minute of the development is documented. The resulting game of the gamejam is here: https://zylinski.itch.io/the-legend-of-tuna
• CAR RACER prototype: https://www.youtube.com/watch?v=KVbHJ_CLdkA
• "point & click" prototype: https://www.youtube.com/watch?v=iRvs1Xr1W6o
• Metroidvania / platform prototype: https://www.youtube.com/watch?v=kIxEMchPc3Y
• Top-down adventure prototype: https://www.youtube.com/watch?v=cl8EOjOaoXc

Atlas builder

The template works nicely together with my atlas builder. The atlas builder can build an atlas texture from a folder of png or aseprite files. Using an atlas can drastically reduce the number of draw calls your game uses. There's an example in that repository on how to set it up. The atlas generation step can easily be integrated into the build bat / sh files such as build_hot_reload.bat

Questions?

Ask questions in my gamedev Discord: https://discord.gg/4FsHgtBmFK

I have a blog post about Hot Reloading here: http://zylinski.se/posts/hot-reload-gameplay-code/

Have a nice day! /Karl Zylinski