This is a neat little puzzler! I dig the strong board-game theme you've got going, though it makes it a little hard to read the puzzles at times. Maybe take some inspiration from playing gameboy games on a gameboy color and choose a secondary color scheme for moving sprites?

Also, I think the level design could use a little work. Right now I felt like there were two massive difficulty spikes, the one where there was a 1 unlock in the top left corner and the penultimate one. Especially the penultimate one took me ages to understand what was even going on, and I think the mechanic behind it had'nt really been explained before (i.e. the fact that once you slide, you have to end up on an empty square)? Maybe that needs a little more buildup. The other levels felt either tutorial-y (which is good) or gimmick-y (which is fine).

Anyway, I think this idea could be worth expanding on, definitely worth checking out!