Kids shouldn't be allowed to play on the stairs. (Too dangerous!) Adults, on the other hand, just need a good reason. This colourful interactive game played with bouncy balls and flashing lights might just be the reason you need.
The game had humble roots, having been originally set up in a stairwell next to the car park of a former industrial building outside Paris. The rules are very simple: you drop a bouncy ball down the stairs, and you get points for each stair you hit. Each of the stairs light up after the bouncy ball hits it so you know where to aim, and if you hit an illuminated stair again, all of the stairs go dark again.
The sad part about this very joyful-looking game is that it doesn't seem to exist outside of these artists' installation. The creators are also vague about how exactly it works, so it's not as easy to replicate on your own stairwell. But imagine if it were just a game that required a Kinect and a projector. You could have whole tournaments without wasting a penny! Or just turn it into a drinking game. In fact that's almost certainly what would happen. [Prosthetic Knowledge]
GIF via Soixante Circuits