PC
Press the Windows logo key 
+PrtScn. The file is saved to the Screenshots folder in your Pictures folder. You can also us the Snipping Tool which is available in all versions of Windows Vista, 7, and 8 except the Starter and Basic editions.
Mac
To take a screenshot with your Mac, Command + Shift + 3 and then release all keys to captuer the whole screen, or press Command + Shift + 4 and press down and drag the mouse over the area you'd like to capture.
iPhone/iPad
To take a screenshot with your iPhone or iPod Touch, press and hold the sleep/wake button and then click the Home button.
Android
Take a Screenshot with Android 4.0 (Ice Cream Sandwich) just press and hold the Volume Down and Power buttons at the same time.
Anonymous stuck on Paper Fold Level 20 walkthrough
chao Lam created levels for Paper Fold