paperjs tutorial, part 2
Part 1 is here: https://github.com/ucsd-cse-spis-2016/spis16-webapps-paperjs
See: https://paperjs.org
Built on top of example webapp from part 2 of the webapps tutorial at http://ucsd-cse-spis-2016.github.io/webapps/webapps-intro-part-2/