Pretty nice soko-like, with nice puzzles (couldn't get past level 8). The atmosphere is very well crafted, both through graphic art and music. It lacks a way to speed up movement to speed up solving.
I saw a few bugs (I payed the web version) : push animation keeps playing when holding directions after pushing a box or against a wall.
The way the players move when there are two of them : in the situation shown in the screenshot below, pushing quickly right-left-right causes the top character to move 2 right and the bottom character to move 1 left, which should not happen according to the established rules, my guess is that your player controller has some logic issues.
No undo is kinda rough, especially on complex levels, but I know it's really hard to implement, especially when custom mechanics are implemented.