There are a few things that Excalibur does that are good to know before you start building games!

Conventions

1. Excalibur uses a theater metaphor, for example: Scenes, Actors, and Actions.

2. Excalibur uses Resources to load external files like images and sounds. They can also be used to load other things like data or config.

3. The negative y direction is up, and the positive y direction is down.

4. Distance units are in pixels, velocity in pixels per second, and acceleration in pixels per second per second.

5. Rotation units are in radians.

6. All elapsed times and durations in Excalibur are in milliseconds.

7. Actor z-indices follow the browser way of doing things.

   • Things with larger positive numbers are on top of lower numbers.

8. Coordinate Spaces

   • World space is the pixel position where Entities and Actors live by default.
   • Screen space is the pixels on the canvas element viewport according to the browser.
   • Page space is pixel offset from the top left of browser window
   • Local space is relative to a parent Entity or Actor

9. Things are in "world" space unless specified with a local prefix or added as a child actor.

10. Bounds are always an axis aligned bounding box, meaning a non-rotated box.

11. Excalibur handles offscreen draw culling for you! No need to manage that!

12. Excalibur uses pre-multiplied alphas when drawing which is important to know if you use Material

API Naming

• Boolean properties describing what an object is or has are named isX/hasX, read-only or settable: actor.isKilled, engine.isRunning, graphics.isVisible, tile.isSolid. Options use the same name: new Actor({ isVisible: false }). Test: if "the object is ___" is a natural sentence, use isX.
• Booleans that name a behavior to perform, or mirror a web platform property, keep their plain name: sound.loop, sound.muted, graphics.smoothing, flipHorizontal. Text formatting attributes follow CSS and typography vocabulary (font.bold, font.family), and common computer jargon like enabled is also left as is.
• Anything that has a side effect or does real work is a verb method: engine.start(), contact.cancel(), input.setEnabled(false).
• Async state is a Promise property, never isX(): await engine.ready, await track.done. The synchronous check is engine.isReady.
• Compound words are spelled consistently: offscreen is one word, matching OffscreenCanvas (isOffscreen, OffscreenSystem), while "on screen" splits in camelCase (isOnScreen, forceOnScreen, onScreenOnly). The acronym stays HiDPI (isHiDPI).