Thank you. I made it to level 20.
As far as I'm concerned, when solving a single-stroke puzzle like this, the play style is more "just move and think haphazardly" than "plan perfectly in advance". This is especially true since many of the levels in this game are very wide.
In that case, missing a square can be a strong frustration. In this game, you have to step on all the squares marked with X. Since the squares marked with X are the same color as the other squares, it is easy to overlook them.
The squares floating up and down are also beautiful as an expression, but they obscure the connection between the squares.
Also, as you progress through the levels, there are no more gimmicks, no distinctive inconsistent levels, just larger and more complex puzzles.
This made the game seem like a repetition of the same thing and I got a little bored. The cost of redoing a large level is significant, and the aforementioned mistakes due to oversight can reduce motivation.
Overall, however, it's a great game.