1. We haven't added support for mobile devices so it won't work if you are trying to play from a browser on mobile devices.
2. If you are playing on a browser on PC, then you'll have to click inside the game window and use arrow keys to navigate the menu and enter/space bar/z to select the "start" button.
3. In the Windows build, there aren't any issues that we know of in terms of starting the game. If you're experiencing any problems in the Windows build, then let us know.