I think there are two distinct kinds of problems in the world
Simple problems are ones that have known solutions, and just require some combination of (effort + discipline + experience) to implement this solution.
Complex problems are ones that have unknown solutions and require the application of imagination / vision to transform them into simple problems before they can be acted upon.
He who wonders discovers that this in itself is wonder. --escher
Project I did after my apprenticeship to consolidate my experiences making auth-gems.
A group final project for DBC, built in 8 days. My role was implementing Backbone models, rebuilding the D3 visual to use model data, getting data from D3 element to display on mouseover, setting up heroku, setting up sessions, and basic crud for guests.
A console tic-tac-toe game, but one with an injected interface so it can be easily adapted to other formats. Hard is unbeatable, while easy is random and medium is in-between.
The code challenge I did for my application to Cover My Meds apprenticeship, the most interesting parts of which are the JS.
Another old code challenge which I kata'd to become more comfortable with Java.
This was an old code challenge I had which I kata'd a few times to learn Java.