The sokoban + portal mecanic works extremely well. It's intuitive and deep which is what make puzzle mecanics great. And I don't think I ever seen it before (and I played sokoban inspired games a lot).
The level design was very good too, although the difficulty curve was a bit rough and some medium difficulty levels were needed between the very easy ones and the relatively hard ones (it's not an issue for people who are used to sokoban inspired games, but in the general public a lot of players will abandon).
The art and audio are good too.
One if the best games I rated.
Beside the difficulty tweeking, IMO the only things that need to be improved are QoL:
* an undo last move button
* a reminder to tell wich door correspond to wich key because it's easy to confuse them.
* arrow keys support, gamepad support, non-qwerty keyboards support
* a skip dialog button
You should submit this game to coolmathgames after you fix the QoL and difficulty curve. It's the kind of game they like and you will earn some money (I sold a sokoban inspired game to them in the past).