Good things:
Graphic style is "tiny" (or chibi if you preffer) You have tiny knight fighting tiny bats. It gives you a great feeling.
Music and sfx is enjoyable which is another great thing because with other games first thing I do is look for mute button. You know there was a lot of work put into this game and as a player I can feel it.
I liked the chest-key system. Really reminds me of Binding of Issac. Actually the whole game feels like Binding of Issac in compact version.
Bad:
I don't really feel encouraged to play the game. After lv 33 I got bored and quit(That's why 3.5 not 4 stars). There were quite often moments when I was just looking for timer to speed up. No enemies on screen. Spikes around me. All I need to do is wait for portal to open. Waiting, waiting, waiting... open! It's ok if it happens once in a while but it was in half of the rooms.
I had difficulties at first to udnerstand what is the deal with portal and red skulls(not protal). OMG skull better not step on that. But I have to... I think the skull is suggesting too strongly that it is something bad instead of marking lack of something good (like cross or no entry signs).