As far as self-study is concerned, it is closer to entertainment than to education (and ultimately just an ad for brilliant.org). But it is a great educational

As far as self-study is concerned, it is closer to entertainment than to education (and ultimately just an ad for brilliant.org). But it is a great educational tool for e.g. a classroom or a math circle led by an experienced mathematician. Discussion about why these puzzles are solvable and when, and how you can build your own, naturally illuminates concepts such as the intermediate value theorem, simply connectedness, and even measure.