Pausing: Control + P (thank you Colorized!)
Press F10 or Alt. Only works in windowed mode. (Note: if you lose focus of the game (i.e. switch to another window) the game will automatically unpause.)

Title Screen: Press F2 to go back to the Title Screen.

Windowed Mode: Press Alt+Enter. Press again to go back to Full Screen.

Exit Simulations: Press Tab. Exits both terminal simulations (where the rabbit follows you) and the main platforming simulations the derelicts are running.

Exit Game: Press Esc. Sends you to your desktop.


Notes:

• "Pausing" is actually just the shortcut for selecting the hidden "File" drop down menu. Press the down arrow key after to see the available options under the "File" menu such as minimizing, maximizing, and closing the game
  
  
• I prefer using F2 instead of pausing in most situations because it's quicker than exiting and reopening the game and I don't have to worry about the game unpausing