if (isThrusting != moveVertical > 0) {
			isThrusting = !isThrusting;
			engines.SetActiveRecursively (isThrusting);
		}

		if (isRetro != moveVertical < 0) {
			isRetro = !isRetro;
			retros.SetActiveRecursively (isRetro);
		}

		if (isThrusting) {
			foreach (ParticleRenderer renderer in engineRenderers) {
				renderer.lengthScale = 4.0f * -moveVertical;
			}
			engineLight.intensity = 8.0f * moveVertical;
		}

		if (isRetro) {
			foreach (ParticleRenderer renderer in retroRenderers) {
				renderer.lengthScale = 6.0f * -moveVertical;
			}
			foreach (Light light in retroLights) {
				light.intensity = 8.0f * -moveVertical;
			}

		}