The Chess Clock has an orientation based interface. In vertical mode you can enter the desired time for each player, or you can use the five or ten minute default button. Then turn the phone to the horizontal mode to see the clock interface.
The clock interface is a single button that switches color to indicate the current player’s turn. In case of accidental flip during play, the clock saves and displays the remaining time, then resumes upon returning to the horizontal. Try with TestiPhone