This is a collection of materials for hack days that work. They are organised into groups and each folder holds material of roughly the same level of complexity. The colour scheme used mirrors that of ski slopes in which green slopes are easy beginner territory from which one can advance through blue and red to reach the black slopes where the terrain is much more challenging.
You might find a specialised code editor helpful. Here are some examples.
All the exercises are designed to use only a web browser, javascript, and some data. If you're new to Javascript check out http://eloquentjavascript.net/ as a good introduction. Another is http://javascriptissexy.com/how-to-learn-javascript-properly/. JSFiddle is also a useful resource to test out javascript and to find handy code snippets. A set of more thorough tutorials is available from Google: https://developers.google.com/web/fundamentals/.
Once you have a suitable editor and have found the javascript help resources the best place to start is to go to the wiki which has some guidance on how to make progress with the hack day exercises and also provides further information about javascript libraries and sources of open data that will be helpful in working through these exercises and also for developing your own work.