Simple jumping box using LKGE

Test.java

package logikers.lkge.test;

import logikers.lkge.components.*;
import logikers.lkge.core.*;
import logikers.lkge.math.Rect;
import logikers.lkge.math.Vector2;
import logikers.lkge.physics.Collision;
import logikers.lkge.physics.PhysicsType;
import logikers.lkge.physics.Polygon;
import logikers.lkge.scenegraph.Entity;
import logikers.lkge.scenegraph.Scene;

class PlayerController extends Physics {

	public boolean grounded = false;
	public float speed = 10;

	public PlayerController() {}

	@Override
	public void init() {
		super.init();
		setPhysicsType(PhysicsType.DYNAMIC);
	}

	@Override
	public void update(float dt) {
		if (Input.getKey(Input.KEY_LEFT)) {
			applyForce(new Vector2(-1, 0).mul(speed * 100).mul(dt));
		} else if (Input.getKey(Input.KEY_RIGHT)) {
			applyForce(new Vector2(1, 0).mul(speed * 100).mul(dt));
		}
		if (grounded) {
			if (Input.getKeyDown(Input.KEY_SPACE)) {
				applyImpulse(new Vector2(0, -1).mul(speed), new Vector2());
				grounded = false;
			}
		}
		super.update(dt);
	}

	@Override
	public void collisionEnter(Collision c) {
		if (c.hitEntity != null) {
			if (c.hitEntity.getTag() == "GROUND") {
				grounded = true;
			}
		}
	}
}

public class Test {

	public static void main(String[] args) throws InterruptedException {
		Game g = new Game();

		Scene sce = g.getCurrentScene();
		Entity box = sce.createEntity(-1);
		box.setTag("BOX");

		Entity camera = sce.createEntity(-1);
		Camera cam = new Camera();
		cam.setZoom(1);
		camera.addComponent(cam);

		g.setAssetManagerCallback(new AssetManagerCallback() {
			@Override
			public void preload(AssetManager assets) {
				assets.addTexture("box", "res://logikers/lkge/resources/box.jpg");
			}

			@Override
			public void finished(AssetManager assets) {
				SpriteRenderer spriteRen = new SpriteRenderer(assets.getTexture("box"));
				spriteRen.getOrigin().set(0.5f, 0.5f);
				box.addComponent(spriteRen);

				CollisionShape box_s = new CollisionShape(CollisionShape.ShapeType.POLYGON);
				box_s.setPolygon(Polygon.createRect(new Rect(-32, -32, 64, 64)));
				box.addComponent(box_s);

				box.addComponent(new PlayerController());

				box.setPosition(new Vector2(0, -200));

				Entity floor = sce.createEntity(-1);
				floor.setTag("GROUND");

				CollisionShape floor_s = new CollisionShape(CollisionShape.ShapeType.POLYGON);
				floor_s.setPolygon(Polygon.createRect(new Rect(-512, -10, 1024, 20)));
				floor.addComponent(floor_s);

				Physics sb = new Physics();
				floor.addComponent(sb);
				floor.setPosition(new Vector2(0, 70));
			}
		});

		App.setGame(g);
		App.start("Testing", 640, 480);
	}

}