How do you beat floor 15 in 100 floor app?

The key to solving the puzzle on level 15 of 100 Floors is the tic-tac-toe shaped marking on the door, and the symbols directly over the door.

Look at the symbols as parts of the board; the first one looks like a backward "L", that's what the upper right corner of the game board looks like, so tap the "1".

Next is a shape that looks like a "C", that matches the shape around the number "6", so tap that.

After that is what looks like a backward "C", and that matches the shape around the "4".

Finally the "L" shape matches what's around the "3", tap that and you've solved level 15 of the game.

100 Floors was released in early May, quickly hitting #1 in the Apple App store.

It's been updated several times since then, bringing it from 30 to 70 levels on June 5, and the game was also finally ported to run on Android devices along with the iPhone, iPod Touch, and iPad.