The Pause Game menu item (also keyboard control-Z) pauses or resumes games in progress.
Player Menu | Pause Game:
A game paused in progress:
The game will also automatically pause if you go away from the keyboard or stop using the mouse for a short time. This is to prevent your tadpole family from all expiring while you go away from the computer for a little bit. When the game is paused your Time Bonus stays the same and your tadpole count remains unchanged.
'Resume' - restarts the game in progress
The game resumed: