Amazing game! I couldn't get past level 4 but I really like the hidden strategies in this game, in that sometimes you want to delay pushing a block or pick up a key to "keep it in reserve" for moves in the future. Also it was super cool that you can leverage the objective (the flag) as part of the strategy.
The only slight nitpick would be that once you have a lot of configurations that were visited once, it goes out of the screen and you can't scroll back to look at where you've already stepped.