This is an entry in the 12th Fortnightly Topic Challenge
Inspiration from @BMyGuest's puzzle
After keying in your answer, the screen goes dark, and emits a BEEP!
You step back as a door swings in front of you, to reveal... a dark room. As you step across the threshold, the door swings shut with a click. A light turns on, slowly getting brighter. As your eyes adjust, you see that there is a wall in front of you, with a tiled floor visible through a doorway.
You turn around and try the door. Naturally, it's locked. What did you expect?
With no other options, you walk over to the doorway, and look at the floor. This is the sight that greets your eyes:
On the far wall, there is a sign that says:
The third clue is hidden here. You must follow the path. Beware - if you step on a wrong tile, there are a lot of things thought up by a twelve year old that can kill you. You start at the tiles marked
Start here, at the bottom left.
I go diagonally exactly once in the puzzle. That time is in a crucial part of the path.