The classic Atari Pong game from 1972, written in Javascript & rendered on a HTML5 Canvas.
Why? Just because. Well, OK, partly because I wanted to refresh my rusty JS skills, partly as a fun exercise to work through with my daughter, and partly because games were the reason I first got into computers as an 8 year old myself, but I haven't actually done any game coding for .... sheesh, about twenty years.
So don't expect this to be a shining example of best practice, more of a testbed for some approaches.
The Javascript uses Classes, so according to MDN it won't run on Internet Explorer, but should run on Edge and all other 'modern' browsers.
You'll need to run a local HTTP server, to get round the CORS restrictions on loading Javascript via file:// URLs. I use Node http-server myself.
Once http-server is installed, just run:
http-server -c-1
from the root directory, and load http://localhost:8080/ in your browser.
Click 'Play' to play. Default controls are:
player 1 - W up / S down
player 2 - up arrow up / down arrow