private void updateForces() {
            keyForce.set(0.0, 0.0);

            if (up && !down) {
                keyForce.offset(0, SPEED);
            } else if (down && !up) {
                keyForce.offset(0, -SPEED);
            }
            if (left && !right) {
                keyForce.offset(-SPEED, 0);
            } else if (right && !left) {
                keyForce.offset(SPEED, 0);
            }
        }