I've seen this before in an minecraft illusions video, and it looked pretty awesome when I first saw it. It's really simple when you think about how it's possible. When you get the trick, you'll laugh. Trust me xD
I've seen something kinda like this, but with random blocks placed, and then if you moved into a spot they show words. All in all this is really cool. :)
Nice. Reminds me of the thread I made awhile ago http://itsjerryandharry.com/threads/accidental-optical-illusion.73766/
It's better to draw the illusion triangle on scrap paper and leaving it on the desk for others to see ( ͡° ͜ʖ ͡°)