A fast, interactive implementation of Conway's Game of Life using vanilla Javascript / HTML5 canvas that I created as an interactive background for my website (You need to press the chip icon next to the purple button!):
I was updating my personal webpage and thought an interactive background would be cool. Remembering the classic tweet that Eben Upton sent to the BBC Micro Bot inspired me to try one based on Conway's Life. Note there are more playable implementations, and better optimized ones too (see Hashlife).
ArcadeLife is fully interactive, runs 60fps @ 4K on a reasonable machine and is fun to play around with for a bit, which is what I needed it to be :)