It's amazing how a tiny design tweak can have such a dramatic impact on an otherwise stellar game. First of all, the pixely art style was great and really meshed well together. It looked and felt like a true homage to other old-school dungeon crawlers.
The controls... well, at first I raised an eyebrow at your choice. You chose to make the entire thing click based. Okay, so instead of using my arrow keys to duck in and out of combat, I just have to click everywhere I want to go. Not the best schematic in my opinion, but moving on.
The permadeath. I like permadeath in games. It makes the deaths feel real and adds tension to each battle. But for the love of all that is good and holy, WARN YOUR PLAYERS FIRST! There isn't even any hints that death will be permanent. In fact, you even lead your players to believe that there's a handy saving function after each world. When I beat the first world my computer froze up for a few seconds, and then told me that you'd saved the game. "Oh good," thought I, "I can now explore the dungeon a little more carelessly now that I- oh, wait, I'm dead. WHAT DO YOU MEAN IT DIDN'T ACTUALLY SAVE!? ARGBVHDBR"
Aaaand now I don't want to play again. So while your team probably spent a lot of time polishing out those later worlds, you just robbed a bunch of players from ever being able to see them.
Of course I'm not going to give this game a 0 for that. Obviously, this is a very high quality game. But rethink the controls and that death system maybe. At the very least, don't dick your players over.