Suiwo, the disciple of Hakuin, was a good teacher. On a certain day a certain pupil came to him, and Suiwo gave him the problem, "Hear the sound of one hand."
The pupil remained three years, but could not pass the test. One night he came...
"Ever had that sinking feeling in the pit of the stomach when you've done or said something stupid? Ever put your foot in it and wished you could turn back the clock those few vital seconds? Well now you can! All it takes is a simple high-risk surgical procedure to implant the facePalm™ button in the forehead. Made a stupid mistake? Simply slap your forehead in the usual manner to activate Apple's revolutionary facePalm™ button, and undo your last action. It's as if all human evolution has been leading up to this moment."
Knocked over an expensive vase? facePalm™!
Spilled coffee on your keyboard? facePalm™!
Heard the door slam as you locked yourself out of the house? facePalm™!
Accidentally insulted the bride at a wedding? facePalm™!
Hit 'send' on an e-mail and immediately regretted it? facePalm™!
Told the wife/husband/girlfriend/boyfriend they could lose a few pounds? facePalm™!
Note: The facePalm™ is powered by unique tachyon energy which is a by-product of the large Hadron Collider. Each undo requires 7 trillion electronvolts. Please do not use near heavy machinery or animal/plant life.
Warning: Hitting the facePalm™ undo button more than three times in a row may damage reality. Please do not attempt to travel back 30 years and change your career or marriage as this may tear a hole in the SpaceTime Continuum.