The Second Layer of the Levels

There are doors in the levels now that take you to a second back layer. They're usually just a little sort of shortcut to somewhere else in the level. And then on top of that, if you find the key now, you have to take it to the chest,. which is always in one of these doors and is always in a room by itself to get the watch at eye. As far as I could tell, I think the entire back of the level is interconnected. It has rock that you can't blow. You can't bomb through, but sometimes you would go to the back path and you would see something like an area you couldn't get to. That sounds super cool.