Cute and challenging puzzle platformer! I wish my attack range was a little bit longer, cause often I'd miss monsters by a pixel or two and then get killed before I could attack a gain. Speaking of pixels, the sprites don't always line up with the pixel grid of the backgrounds: 
Enemy death animations (the rotation) also looks a bit goofy and not quite NES-like. And the game is force scaled to such a high resolution it doesn't quite fit in my browser window, so I had some overscan issues, lol! Otherwise, quite good!