In my opinion, the thing that makes these puzzles different from bog-standard code challenge sites is simple, but profound: 'the twist'. Each day's puzzle is n

In my opinion, the thing that makes these puzzles different from bog-standard code challenge sites is simple, but profound: 'the twist'. Each day's puzzle is not one, but two-fold. You first solve the problem you're given, and then the second half is unlocked. /This second half usually incorporates some sort of twist./ That means that you may have to rethink your program, generalize it, find some missing optimization or think your way around the problem as it's given, etc. In some ways, it feels like what you have to do to a real program: You write what you think is a perfect solution, then discover you need to model the problem more deeply, or refactor it all, or scrap it and start over. It's a flavor of 'puzzle realism' that makes each day a bite-size nugget of a challenge that's genuinely fun to work out.