There's no mining happening in the browser. My inspiration was CSI's "visual aids", where a computer will look like it's grinding through a database but not act

There's no mining happening in the browser. My inspiration was CSI's "visual aids", where a computer will look like it's grinding through a database but not actually be doing any work. So the red "random" hashes are exactly that: random numbers. The site just listens out for broadcasts on the Bitcoin network, and displays them when they show up.