It is important that you play this. It's free, so you've got no excuse. Not even that you're colourblind or deaf, because it's designed to be playable regardless of colour or audio cues.
Fotonica is loosely an auto-running game, in the vein of Canabalt or Robot Unicorn Attack, but with tasty dollops of Mirror's Edge and Rez mixed in to create something hallucinatory, abstract and balletic. And all with one button.
Essentially, it's a timing-based jumping game. Hold down a button (any button) to run, release it to jump, hit it again to land. Sich a prosaic, mechanical description doesn't do it justice, however: it's very much about the fuzzy line-art look and whispered electronic music. These things add a sense of place and imperative that mere button-pushing and score-chasing simply could not.
I am, in time-honoured fashion, rubbish at it. Doesn't stop me from going back for me.
I will advise that you pop into its settings and turn off 'arms' before you play though. The big, dangly wireframe hands rather detracted from the experience for me, but by making it toggleable I suspect Italian devs Santa Ragione were aware that could be the case.
It's browser-playable, but requires the Unity plugin so someone's gonna do the usual and become shocked and outraged that this PC gaming site is posting about a Windows game again, like we've been doing every day for three years. For those who can't/won't play it, here's what it looks and sounds like. Do play it though - the tension and gravitational panic is a vital part of the experience.
Oh, and I do love Santa Ragione's solemn pledge: "We like the ugly 3D of the '90s and will bring you more!" I look forward to it.