smartgame/js/entities/FloatingPlatform.js

import Entity from "../Entity.js";
import Texture from "../Texture.js";
import Tile from "../Tile.js";
import assets from "../assets.js";

import TPlatform from "../traits/TPlatform.js";
import TCollider from "../traits/TCollider.js";
import TPhysics from "../traits/TPhysics.js";

export default class FloatingPlatform extends Entity {
	constructor(level, width = 5) {
		super(level);

		this.bounds.size.set(width, 0.5);
		this.addTrait(new TCollider(this));
		this.addTrait(new TPlatform(this));
		this.addTrait(new TPhysics(this));

		this.texture = new Texture(assets.tiles,
			Tile.createLine(this.bounds.size.x, "platform"));

		this.targetSpeed = 3;
		this.accel = 5;
		this.dir = 1;
		this.distance = 5;
	}

	init() {
		this.targetTop = this.bounds.pos.y;
		this.targetBottom = this.targetTop + this.distance;

		this.t.physics.gravity = 0;
		this.t.physics.velocity.y = 0;
	}

	update(dt) {
		let phys = this.t.physics;

		if (this.bounds.pos.y <= this.targetTop)
			this.dir = 1;
		else if (this.bounds.pos.y >= this.targetBottom)
			this.dir = -1;

		if (this.dir == 1) {
			if (phys.velocity.y < this.targetSpeed)
				phys.velocity.y += this.accel * dt;
		} else {
			if (phys.velocity.y > -this.targetSpeed)
				phys.velocity.y -= this.accel * dt;
		}
	}

	draw(ctx) {
		this.texture.drawAt(ctx, this.bounds.pos);
	}
}