Humanity desperately needs the invention of a door that humans can open and pass through *without* enabling cats to zoom by in or out at the same time. This is likely to involve 4th or higher dimensional physics.
Huh? I mean a simple ladder going to a hatch in the ceiling (instead of a staircase and a door). You don't need to use your arms for anything other than balance on typical ladder.
@robryk @lauren I was thinking a more vertical ladder -- E.g., something skin to rungs running up a wall.