@rpgjs/physic/dist/index35.js

A deterministic 2D top-down physics library for RPG, sandbox and MMO games

class Knockback {
  /**
   * Creates a knockback movement.
   *
   * @param direction - Direction of the impulse (will be normalized)
   * @param initialSpeed - Initial speed in units per second
   * @param duration - Duration in seconds
   * @param decayFactor - Fraction of speed preserved per second (0-1)
   */
  constructor(direction, initialSpeed, duration, decayFactor = 0.35) {
    this.duration = duration;
    this.decayFactor = decayFactor;
    this.elapsed = 0;
    const magnitude = Math.hypot(direction.x, direction.y);
    this.direction = magnitude > 0 ? { x: direction.x / magnitude, y: direction.y / magnitude } : { x: 1, y: 0 };
    this.currentSpeed = initialSpeed;
  }
  update(body, dt) {
    this.elapsed += dt;
    if (this.elapsed <= this.duration) {
      body.setVelocity({
        x: this.direction.x * this.currentSpeed,
        y: this.direction.y * this.currentSpeed
      });
      const decay = Math.max(0, Math.min(1, this.decayFactor));
      if (decay === 0) {
        this.currentSpeed = 0;
      } else if (decay === 1) ;
      else {
        this.currentSpeed *= Math.pow(decay, dt);
      }
    } else {
      body.setVelocity({ x: 0, y: 0 });
    }
  }
  isFinished() {
    return this.elapsed >= this.duration;
  }
}
export {
  Knockback
};
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