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.
@lauren Isn't metal ladder and a horizontal hatch a reasonable approximation?
@robryk A bit inconvenient for routine use, me thinks.
@robryk @lauren I was thinking a more vertical ladder -- E.g., something skin to rungs running up a wall.