When starting a game on your phone, the program should detect that you are on a smaller device and automatically offer you the following options:
- Full screen mode
- Large print tiles
We definitely recommend accepting both of these options. Also make sure that "orientation lock" is off and rotate your phone into landscape orientation.
The above should ensure that the game takes up the entirety of the phone's screen.
Unfortunately, some iPhones do not support fullscreen mode, and will keep showing a bar at the top and/or bottom, taking up valuable screen space. You can shrink the bar by tapping AA (left of the address bar) and selecting "Hide toolbar".