1. Quit it
Your software may be stalled.
On PCs, hold down the Ctrl+Alt+Delete keys to open the task manager. Select the " not responding" program; click "end task".
On a Mac, use Command+Option+Esc
2. Still frozen?
PC: Hit Ctrl+Alt+Delete again, or hold down the power key.
Mac : Command+Shift+Option+Power.
Last-ditch effort: Force a shutdown by unplugging or removing the battery. Wait a minute, re-plug, and restart.