The hotel bathroom puzzle
I'm reminded of a discussion we had here a few weeks ago, where somebody noted that humanity wouldn't be able to invent, for example, a machine to automatically rack pins at a bowling alley today.The 2018 solution to that problem would automatically involve computer vision, AI and robotics.  The idea that one could construct a giant mechanical device the size of an entire bowling lane that is purpose built to lift, sweep, collect, rack, and place pins with no capacity for customization whatsoever wouldn't even occur to today's generation of engineers.You can see it happening in some of the comments here.