This is a fun game by all means, but it has a few problems. As many others have noted, there isn't a difficulty curve, which I wouldn't see as much of a problem if the levels were split up into packs or groups with a general difficulty on them.
Also, the drag and drop mechanics are rather clumsy, and sometimes they fail altogether needing to reboot the game (which happened to me twice).
But while these problems are pretty easy to fix and could be done in a simple update, the biggest issue I have with the game is more of a gameplay based one. The level's aren't designed all that well.
I don't mind that some (well, most) levels have spaces that don't need to be filled out to complete the level, if anything this makes the game far less stressful and an easier experience. However, many levels have enough leftover space to hold one or two extra figures, this particular one had leftover space that could be filled out with a minimum of three figures: https://ibb.co/g0b8ud
That all being said, there's still a lot of positives. It's simple, clean, and easy to understand; deserving of front page at least, so bravo on all that :)