input

Input

Every way a person can touch a game — finger, mouse, pen, key — arrives as one replayable stream of intents in tile coordinates, bucketed to simulation ticks, behind one object that unbinds all of it.

The two properties that shape everything else:

• Input never learns what is in the world. There is no registry, no rect, no pickable flag and no hit callback — so an implementation that caches hit boxes during the draw pass cannot be built on it, because there is nowhere to put them and nothing that would read one. (In the source game that cache made every collect bubble untappable in a backgrounded tab.) terrain is not an exception: a heightfield is the shape of the ground, a parameter of the projection in the same sense the camera is, and no hit box can be stored in one or recovered from it.
• Gestures are delivered on simulation ticks, never on frames. So a tap cannot be dropped by a slow frame or fired twice on a fast one.

The five lines a game writes

import { createInput } from '@latticekit/input';
import type { Camera, HeightField } from '@latticekit/iso';
import type { Loop } from '@latticekit/loop';

export function wire(
  canvas: HTMLCanvasElement,
  camera: Camera,
  loop: Loop,
  land: HeightField,
  maxHeightPx: number,
): void {
  const input = createInput({
    element: canvas,
    camera,
    step: loop,                    // the loop itself, so the step cannot drift
    terrain: { field: land, maxHeightPx },   // or 'flat'. Never nothing — see below
    actions: { place: ['tap', 'key:Space'], cancel: ['key:Escape'] },
  });

  input.onAction('place', (a) => {
    if (!a.onGround) return;       // the pointer was on the sky: gx/gy are NaN
    void a.gx;
    void a.gy;
  });
  loop.onUpdate((_dt, tick) => input.tick(tick));
  loop.onRender((_alpha, _time, nowMs) => input.frame(nowMs));

  // Under Vite: without this a hot reload leaves a zombie game drawing and not responding.
  if (import.meta.hot) import.meta.hot.dispose(() => input.dispose());
}