Platformer controller

import {  bool,  CharacterController2D,  defineInputActions,  f32,  Script,  SpriteAnimator,  SpriteRenderer,  Vec2,} from "ignifx";import type { InputAction, MutableVec2, ScriptCallbacks, Tilemap } from "ignifx";/** * The runner: everything about how the character *feels*, in one file, so `main.ts` is only the * scene it stands in. * * `CharacterController2D` is a kinematic box that collides and slides through Rapier and applies no * gravity of its own. That is what makes this script possible: it owns the vertical velocity, and * with it coyote time, a jump buffer, a variable jump height, and dropping through a plank. *//** Below this height the runner has left the world through the pit, and is put back. */const FALL_LIMIT = -2;/** The actions the runner reads. Its own map, so the kit's camera actions are untouched. */export const RUN_ACTIONS = defineInputActions({  maps: [    {      name: "Course",      actions: [        {          name: "move",          type: "vector2",          bindings: [            {              composite: "2DVector",              up: "<Keyboard>/w",              down: "<Keyboard>/s",              left: "<Keyboard>/a",              right: "<Keyboard>/d",            },            {              composite: "2DVector",              up: "<Keyboard>/arrowUp",              down: "<Keyboard>/arrowDown",              left: "<Keyboard>/arrowLeft",              right: "<Keyboard>/arrowRight",            },            { path: "<Gamepad>/leftStick", processors: ["deadzone(0.2)"] },            { path: "<Gamepad>/dpad" },            { path: "<Virtual>/joystick", processors: ["deadzone(0.15)"] },          ],        },        {          name: "jump",          type: "button",          bindings: [            { path: "<Keyboard>/space" },            { path: "<Keyboard>/z" },            { path: "<Gamepad>/buttonSouth" },            { path: "<Virtual>/jump" },          ],        },      ],    },  ],});/** * Runs, jumps, cuts the jump short, remembers a press made just before landing, forgives one made * just after walking off a ledge, and drops through a plank on down-and-jump. * * Input is sampled in `update` and spent in `fixedUpdate`, because those are two different clocks. * `wasPressedThisFrame` is true for exactly one *frame*, and a frame carries zero, one or two fixed * steps: read it inside the step and a press is either missed or acted on twice. */export class Runner  extends Script.define({    /** Top running speed, in metres per second. */    speed: f32(7),    /** How fast the run reaches top speed on the ground, in metres per second squared. */    groundAcceleration: f32(70),    /** The same in the air, where a smaller number means less control. */    airAcceleration: f32(35),    /** The upward speed a jump starts at, in metres per second. */    jumpSpeed: f32(15),    /** Downward acceleration while rising, in metres per second squared. */    riseGravity: f32(36),    /** Downward acceleration while falling; larger than `riseGravity` on purpose. */    fallGravity: f32(52),    /** The fastest the runner may fall, in metres per second. */    terminalVelocity: f32(24),    /** How long after walking off a ledge a jump still works, in seconds. */    coyoteTime: f32(0.1),    /** How long before landing a jump press is remembered, in seconds. */    jumpBuffer: f32(0.12),    /** What the rising velocity is multiplied by when the button is released early. */    jumpCut: f32(0.45),    /** Whether the sprite is mirrored when running left. */    flipSprite: bool(true),  })  implements ScriptCallbacks{  /** The namespaced registration id. */  static typeId = "platformer-controller/Runner";  /** Where the map's objects layer put the runner, and where a fall puts her back. */  spawn: MutableVec2 = new Vec2();  /** The level, so a drop-through can ask what the runner is standing on. Assigned on spawn. */  level: Tilemap | null = null;  /** How many times the runner has been caught by the pit, for the panel. */  falls = 0;  #controller: CharacterController2D | null = null;  #animator: SpriteAnimator | null = null;  #sprite: SpriteRenderer | null = null;  #move: InputAction | null = null;  #jump: InputAction | null = null;  /** The runner's velocity, in metres per second. The script owns it, not the controller. */  readonly #velocity: MutableVec2 = new Vec2();  /** The displacement handed to `move`, and the cell the drop-through reads. Both reused. */  readonly #step: MutableVec2 = new Vec2();  readonly #cell: MutableVec2 = new Vec2();  #wishX = 0;  #wishDown = false;  #buffered = 0;  #coyote = 0;  #jumpHeld = false;  #wasGrounded = true;  #clip = "";  awake(): void {    this.#controller = this.entity.requireComponent(CharacterController2D);    this.#animator = this.entity.getComponent(SpriteAnimator);    this.#sprite = this.entity.getComponent(SpriteRenderer);    this.#move = this.app.input.actions.find("move");    this.#jump = this.app.input.actions.find("jump");  }  update(dt: number): void {    const vector = this.#move?.vector ?? null;    this.#wishX = vector?.x ?? 0;    this.#wishDown = vector !== null && vector.y < -0.5;    this.#jumpHeld = this.#jump?.isPressed ?? false;    if (this.#jump?.wasPressedThisFrame === true) {      this.#buffered = this.jumpBuffer;    } else if (this.#buffered > 0) {      this.#buffered = Math.max(0, this.#buffered - dt);    }    this.#animate();  }  fixedUpdate(dt: number): void {    const controller = this.#controller;    if (controller === null) {      return;    }    if (this.transform.position2D.y < FALL_LIMIT) {      this.falls += 1;      this.#velocity.set(0, 0);      controller.teleport(this.spawn);      return;    }    const grounded = controller.isGrounded;    this.#wasGrounded = grounded;    this.#coyote = grounded ? this.coyoteTime : Math.max(0, this.#coyote - dt);    this.#accelerate(dt, grounded);    if (this.#buffered > 0 && this.#coyote > 0) {      this.#buffered = 0;      if (grounded && this.#wishDown && this.#dropThrough(controller)) {        this.#velocity.y = -6;      } else {        this.#coyote = 0;        this.#velocity.y = this.jumpSpeed;      }    }    // Releasing the button on the way up cuts the rise short. That is the whole of "variable jump    // height": holding it gives the full arc, tapping gives a hop.    if (!this.#jumpHeld && this.#velocity.y > 0) {      this.#velocity.y *= this.jumpCut;    }    const gravity = this.#velocity.y > 0 ? this.riseGravity : this.fallGravity;    this.#velocity.y = Math.max(-this.terminalVelocity, this.#velocity.y - gravity * dt);    if (controller.isGrounded && this.#velocity.y < 0) {      // Parked at a small negative value rather than zero: a growing downward velocity while      // standing still would defeat `snapToGround` on the way down a ramp.      this.#velocity.y = -1;    }    this.#step.set(this.#velocity.x * dt, this.#velocity.y * dt);    controller.move(this.#step);    // The controller reports what it *actually* did. Walking into a wall has to zero the stored    // horizontal speed, or the runner keeps pressing into it and never accelerates away.    const actual = controller.velocity;    if (Math.abs(actual.x) < Math.abs(this.#velocity.x) * 0.5) {      this.#velocity.x = actual.x;    }    if (this.#velocity.y > 0 && actual.y <= 0) {      this.#velocity.y = 0;    }  }  /**   * Whether the runner is standing on something, for the panel.   *   * @returns `true` while the controller reported ground under the box on the last fixed step.   */  get isGrounded(): boolean {    return this.#wasGrounded;  }  /**   * The runner's current speed, for the panel.   *   * @returns The magnitude of the script's own velocity, in metres per second.   */  get speedNow(): number {    return Math.hypot(this.#velocity.x, this.#velocity.y);  }  /**   * Steps down through a one-way plank, if that is what the runner is standing on.   *   * @remarks   * The runtime's rule is "solid only while the character is descending and its feet are at or   * above the plank's top", so the way down is to put the feet below that top — and the way to know   * it is safe is to ask the map. `Tilemap.worldToCell` is exact and free, and `collisionAt` answers   * with the cell's own `oneWay` flag, so a drop-through can never open a hole in solid ground.   *   * A shape query would be the obvious alternative and is the wrong tool: a tilemap's collision is   * a **merged outline**, so `overlapBox` with a small box entirely inside the ground crosses no   * edge and reports nothing (measured 2026-09-08).   *   * @param controller - The controller to move.   * @returns `true` when the runner was moved down through a plank.   */  #dropThrough(controller: CharacterController2D): boolean {    const level = this.level;    if (level === null) {      return false;    }    const feet = this.transform.position2D;    // A tenth of a metre below the feet is inside the cell that is holding them up.    const cell = level.worldToCell({ x: feet.x, y: feet.y - 0.1 }, this.#cell);    if (!level.collisionAt(cell.x, cell.y).oneWay) {      return false;    }    controller.teleport({ x: feet.x, y: feet.y - 0.45 });    return true;  }  /**   * Moves the horizontal velocity toward the wished-for speed at the right acceleration.   *   * @param dt - The fixed step, in seconds.   * @param grounded - Whether the runner is on the ground, which decides which rate is used.   */  #accelerate(dt: number, grounded: boolean): void {    const target = this.#wishX * this.speed;    const rate = (grounded ? this.groundAcceleration : this.airAcceleration) * dt;    const delta = target - this.#velocity.x;    this.#velocity.x += Math.abs(delta) <= rate ? delta : Math.sign(delta) * rate;  }  /** Chooses between idle, run, jump and fall, and mirrors the sprite. */  #animate(): void {    const sprite = this.#sprite;    if (sprite !== null && this.flipSprite && Math.abs(this.#wishX) > 0.05) {      sprite.flipX = this.#wishX < 0;    }    const clip = this.#wasGrounded      ? Math.abs(this.#velocity.x) > 0.4        ? "run"        : "idle"      : this.#velocity.y > 0        ? "jump"        : "fall";    if (clip !== this.#clip) {      this.#clip = clip;      this.#animator?.play(clip);    }  }}

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