Naturally, I began work on it immediately.
DR. FATE'S TOWER
There's a "floor area", where players start, and there are chambers that are "above" the floor area; the two areas are not connected, and each treats the other as blocking terrain (except for the stairs, which floor figures can move past, but not see through). That is, until...!
At the beginning of each players turn, he rolls one die (or, if the players agree to it, two dice). The chamber(s) that corresponds to the number on the die is immediately considered part of the floor (with no walls). Through that chamber, the other chambers can be accessed. Except for the very first "room roll", a player can choose to skip their roll and leave the chambers where they are.
So, exactly where you are and who can see can change with each room roll. Kind of like the wackiness of Dr. Fate's ever-changing tower.
It's a hard environment to plan for, so you want a team that's mobile and adaptable. Powers of particular value would include Stealth, HSS, Running Shot, and Probability Control (which can be used on the room roll).