Automatic doors. What an innovation. Above them, the sensor waits for people to come along. It lights up when it detects someone, and the doors open, generally just a tad late, so you end up slowing down in anticipation of them opening. I’ve been playing with the ones at work. Playing "Chicken" with them. As I come power-walking down the corridor, will they open in time? Will I keep walking beyond the "point of no return", the point beyond which if I walk too fast, they won’t open in time and I’ll get a flat nose?