By Michael Hartley
In this puzzle, a cat is hiding behind a door. Every time you open the wrong door, the cat moves one door to the left or right. He never sits still, he never moves more than one step.
Your goal? Find the cat, opening as few doors as possible! Since the goal is to figure out the best strategy for finding the cat, the puzzle won't tell you if you found him, it will tell you the chance you found him, based on the doors you opened.
So, go on, tap on a door. You'll see below the doors information on how likely it is you found the cat already. If you like, you can show which doors are most likely to be hiding the cat - just click "Show/Hide Probabilities".
Oh, and after you've checked if the cat is there - tap the door again to close it.
I originally saw this puzzle in a blog by a puzzler at the Guardian newspaper. They didn't originate the puzzle, I'm not sure who did. Can you find a way to actually guaranetee