Small purpose-driven projects are good for teaching a lot of things, like connecting different tools to accomplish a larger task. Unfortunately, these sorts of tasks tend to side step more fundemental aspects of computer science, namely important data structures and algorithms.

HackerRank, with its many topic-based challenges, directly exposes the purposes and efficiencies of different algorithms and data structures on large data sets. Whenever I stuggle with a challenge problem, I know there is a larger lesson to be learned, which in turn, guides me to specific topics to study that I otherwise would have been unaware of.

In the more tangible realm, HackerRank offers certification uppon passing a timed assessment. Additionally, a public leaderboard is kept per topic, and badges are awarded for progress and rank. My accolades and stats can be viewed in summary here, or verified on the website.