This feels like an addicting phone game. It's simple and feels almost mindless at first, but is actually well designed to punish impatience and frustration and reward slow and methodical play. Of course, at the same time it has a stopwatch which psychologically primes the player to try and get a "good time".
You should release it as an app and it may just become the mobile version of "Getting Over It" with Bennet Foddy