Its simple, but it works well, especially to pick main theme colours, mrspeaker rightly points out that doing so in a tiny preview window rarely gives you a proper indication. I'm not entirely sure that it actually fits into a designer or css workflow, but it _is_ enjoyable. Plus it appears to be HTML5, so it has electrolytes.<p>A few thoughts (without necessarily providing any solutions!):<p>* While interesting that the logo changes colour, I find that it nearly always picks a gradient which is extremely uncomplimentary to the background. It would be less of a distraction if it was only white/black.<p>* When you click to lock the colour, it would be nice if it could leave a marker to show you where your choice was, so that you could make minor adjustments more easily (I guess the luminosity makes it a little tricky!).<p>* The links for the colours at the bottom of the app say rgb(239,16,146), which would be great for CSS to copy-paste the correct format, but when you click it actually enters '239 16 146'. The hex code is the only one which gives me a useful value straight into the clipboard.<p>* I missed the note about luminosity at first (I count myself as a typical user in that I do not read instructions), it makes sense and works quite well when you actually start scrolling, but is a little hidden.