H = '../media/textures/transparent.png';
    const QUAD_ARROW_MONO_PATH = '../media/textures/arrow-up.png';

    // If requested, use the polyfill to provide support for mobile devices
    // and devices which only support WebVR.
    import WebXRPolyfill from '../js/third-party/webxr-polyfill/build/webxr-polyfill.module.js';
    if (QueryArgs.getBool('usePolyfill', true)) {
      let polyfill = new WebXRPolyfill();
    }

    // XR globals.
    let xrButton = null;
    let xrSession = null;
    let xrRefSpa