A web app in PHP and JavaScript.
Intended use at the time of creation was to practice counting cards, so basic strategy and a hidden Hi-Lo counter is at your disposal.
Click on the dealer's deck to toggle on/off for the Hi-Lo counter.
If you have PHP installed (try "php -v" on command line), you can use the built-in web server to play:
$ cd blackjack/
$ php -S localhost:8080
Now point your browser to http://localhost:8080/ and try to beat the dealer!
It was made years ago and at the time I didn't know enough JS (and jQuery etc wasn't really what it is today), so I made some parts in PHP and the rest in JS.
Could be a nice project to rewrite the entire thing with modern solutions!