This address is not secure. You can play here, but full installation and offline play need a trusted HTTPS address. An HTTP LAN address is not enough.
Android: open in Chrome, then use the browser menu → Install app or Add to Home screen.
iPhone / iPad: open in Safari, tap Share → Add to Home Screen. Leave Open as Web App enabled if that option appears.
Launch from the new home-screen icon, not a browser tab. Fullscreen is requested where supported; some phones keep system status or navigation bars.