Points to play to.
Reserve time per point.
Free seconds each turn. Never carries over.
Marks the player on turn.
Turn change, delay expiry, time out.
Changing match, time or delay resets the clocks. The score is left alone.
Points won, this end of the phone.
Points won, far end.
Changing the score starts a new game: moves back to zero, turn back to the first tap. The clocks keep their times.