private void checkInput(int delta) {
		if (Keyboard.isKeyDown(Keyboard.KEY_UP)) {
			magnitude += delta / 1000.0f;
			if (magnitude > 0.9f) {
				magnitude = 0.9f;
			}
		}
		if (Keyboard.isKeyDown(Keyboard.KEY_DOWN)) {
			magnitude -= delta / 1000.0f;
			if (magnitude < 0.1f) {
				magnitude = 0.1f;
			}
		}
		if (Keyboard.isKeyDown(Keyboard.KEY_LEFT)) {
			period += delta / 1000.0f;
			if (period > 2.0f) {
				period = 2.0f;
			}
		}
		if (Keyboard.isKeyDown(Keyboard.KEY_RIGHT)) {
			period -= delta / 1000.0f;
			if (period < 0.5f) {
				period = 0.5f;
			}
		}
	}