particle.js

import GameObject from './gameobject';

const PI_ON_180 = Math.PI / 180;

const FORCE_MULTIPLIER = 0.8;

export default class Particle extends GameObject {
  constructor(x, y, direction, force, colour) {
    super(x, y, direction * PI_ON_180, null);
    this.force = force;
    this.colour = colour;
    if (this.colour.length < 4) {
      this.colour.push(1);
    }
  }

  update(deltaTime) {
    this.dispatchEvent('update', deltaTime);
    this.x += Math.cos(this.rotation) * this.force * deltaTime;
    this.y += Math.sin(this.rotation) * this.force * deltaTime;
    this.force += this.force * FORCE_MULTIPLIER * deltaTime;
  }

  render(ctx, Camera) {
    this.dispatchEvent('render', ctx, Camera);
    ctx.translate(this.x + Camera.x, this.y + Camera.y);
    ctx.rotate(this.rotation);
    ctx.fillStyle = `rgba(${this.colour[0]},${this.colour[1]},${this.colour[2]},${this.colour[3]})`;
    ctx.fillRect(-2, -2, 4, 4);
    ctx.setTransform(1, 0, 0, 1, 0, 0);
  }
}