| crystal | Functionality related to the entire game. |
| crystal.ai | Components facilitating creation of autonomous entities. |
| crystal.assets | Loads and unloads game assets (images, spritesheets, maps, etc.). |
| crystal.cmd | Allows you to define and run console commands. |
| crystal.const | Allows you to define tweakable variables for fast iteration. |
| crystal.ecs | Implements the Entity Component System pattern. |
| crystal.graphics | Components and classes related to displaying graphics. |
| crystal.hot_reload | Restarts the game every time assets or source files are saved. |
| crystal.input | Manages keybindings and routes input events. |
| crystal.log | Provides an interface to write log messages to console and to disk. |
| crystal.physics | Components allowing entities to move and collide with each other. |
| crystal.scene | Manages game scenes and transitions between them. |
| crystal.script | Coroutine-based scripting system to write logic that takes place over multiple frames. |
| crystal.test | Provides an interface to define unit or integration tests. |
| crystal.tool | Allows you to define visual development tools. |
| crystal.ui | Building blocks to create interactive menus and HUDs. |
| crystal.window | Handles scaling and letterboxing to support arbitrary window sizes. |