This repo extracted the pixel art code from the fun and famous NES.css.
To create your own pixel art, please change the bitmap in scss/mario.scss (or rename to your favorite character :P) and run:
sass --no-source-map scss/mario.scss css/mario.cssthen include the generated css file to your website.
If you would like to edit little by little, you could try:
sass --watch --no-source-map scss/mario.scss css/mario.cssto make the sass compiler recompile automatically upon changes.
Click here for the running Mario in index.html!