> In labs everywhere, experimental robots would leap up from lab benches in a murderous rage, locate the door, and—with a tremendous crash—plow into it and fall over.

> Those robots lucky enough to have limbs that can operate a doorknob, or to have the door left open for them, would have to contend with deceptively tricky rubber thresholds before they could get into the hallway.

https://what-if.xkcd.com/5/