CodePen

I think I’ve written about CodePen before, its a site that allows users to quickly put together HTML, CSS & JS and see the results as they edit. Users ‘pens’ are public and can be tagged, so it also serves as a repository of examples.

It’s possible to host incredibly complex artefacts, such as this 3D Sony Walkman , but what I mostly use it for is to work out simple things - like how to collapse a row of text into a column with a media query.