version: "1.0.0" name: build-app description: Use when creating or restructuring a PlayCanvas app with the Engine API, @playcanvas/react, or @playcanvas/web-components, covering bootstrap, input, resize, physics, update loop, UI, and lifecycle.

Build an Engine application

Read package.json and the entry point, keep the surface that owns the lifecycle, and read only its reference: direct Engine, React, or Web Components. Choose from imports and markup, not dependencies.

Bootstrap

• Input is opt-in. app.keyboard, mouse, touch, gamepads, and elementInput stay null

unless passed to new Application(canvas, { ... }); UI buttons need new ElementInput(canvas).

• The Engine adds no window resize listener; call app.resizeCanvas() from your own handler.
• graphicsDevice.maxPixelRatio defaults to 1. Raise it, at most to window.devicePixelRatio, only

where the target holds its frame budget, call app.resizeCanvas(), and confirm with canvas.width / canvas.clientWidth.

• Rigid bodies stay inert until Ammo loads through WasmModule. Copy the loader from the

physics/falling-shapes example with find-examples.

• devtools defaults to true, so debugging tools can find the app (inspect-runtime). Set it to

false only to hide a production build.

Update loop

• dt is already clamped by app.maxDeltaTime (0.1 s); tune it instead of clamping by hand.

app.timeScale scales it, and 0 pauses scaled time.

• Keep app state explicit and owned in one place; advance time-dependent logic from dt, and reset

through the same setup used at start.

UI

• Render UI from app state; never keep the source of truth in the DOM or UI elements.
• Use a DOM or React overlay, or Engine screen and element components adapted from a

user-interface example.

• Hide unused elements with enabled = false; an element at opacity 0 still draws.

Ownership

• Keep one owner for app creation, assets, entities, update callbacks, and teardown.
• Prefer the surface's declarative primitives. Put per-entity and per-frame behaviour in an Engine

Script.

• Remove external events and resources in the lifecycle that created them.