It's pretty well done. The music was nice and the game was easy to learn and follow. In particular, I enjoyed how the game introduced a new way of finding adjacent blocks with each level, which makes the increase in difficulty feel meaningful. Unfortunately, I wasn't able to complete level 5 as sometimes there were too many changes per step for my brain to figure out.
One thing I'd suggest for the future is to show the colour of the tile underneath the red X marking which tiles the player missed, making it easier to tell where they went wrong. Showing a step-by-step history that the player can flip between would be nice as well.