Quick math game using CSS counters and specified increments. No JavaScript.
Blog post: [Fun Times with CSS Counters](http://codersblock.com/blog/fun-times-with-css-counters/)
Uses a pre made image as the background of the canvas element and draws a user defined line pattern over the top. Position of the lines is determined by cursor position.
See it on a production page: https://squareup.com/gift-cards
Protip - if you're trying to animate background-position for a falling snow animation you're gonna have a bad time. Instead, use hardware-accelerated keyframe animations and handle the looping with duplicate elements.