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I like the traffic light indicators on the floor when I look at my phone
(piefed.jeena.net)
Normally when you need to wait at a crossing because it's red you take out your phone to waste some time. But you have to be quite anxious and look up if it's already green or not, otherwise you miss the green light.
But they help you out with that here in Korea by building in the traffic light into the curb. You're looking down on your phone and see the red line left and right of it. Once it changes to green you immediately are aware of it because it's in your field of view constantly.
Great invention!
I took the background picture just outside and put the stock picture hands with a phone on top of it so you can easier visualize it how it looks like in reality.
In that case I would take my modern device with me that's loaded up with gigabytes of music from the last hundred years, and amaze some king or queen with my magic.
Someone's been reading comments on the zapped back in time post.