This is very nicely done. It works well, both on desktop and mobile. It's well presented and polished. As for the game... At first I thought it was going to be

This is very nicely done. It works well, both on desktop and mobile. It's well presented and polished. As for the game... At first I thought it was going to be just ok. Nothing more than a couple of minutes and then move on. But then I ended playing a bunch of the puzzles in a row without even noticing the time. It plays very, very well and it's quite fun. Congratulations.