Just in time for Halloween, 3spoopy.
Used in many games, skeleton mapping (also like to call it ghost mapping) is the idea of giving properties to blocks that are otherwise normal.
Here's an example of Super Metroid. The triangles allow you to walk up hills, red blocks can be destroyed, some blocks have different heights, some can be jumped through, not all of these are shown in the image.
Although you can see these blocks when editing the game, in the final release, they are all onced 0 alpha, and can only be seen in debug.
In this short example, you will be misdirected through fake walls, fake ground, hills, wind, and passable ground. I was going to make red blocks trigger the block behind to be destroyed, but they can't seem to proximity each other and crash the screen white. I don't know why. I'll look into it. For now, try it out. Get through the level with the debug on, then when you get to the end, redo it with the debug off, and see if you can remember where the collisions were.http://flowlab.io/game/play/742026