Absolutely beautiful pixel art. I think this is about as good as it can get with 4 colors at 160 by 144 resolution! Everything's got animation frames and looks great! It takes real talent to make things sexy at this size! The only thing that bothers me in terms of visuals are the checkered floors and dithered backgrounds, the fast pace of the game makes them flicker too much.
Gameplay is solid and fun. The boss was very disproportionately difficult to the rest of the game, I wasn't even sure if it had a lifebar or if there was some gimmick to taking it out, made my hands hurt. The rest of the game is great and lets you go at your own pace. I don't think you should spoil the different items and enemies in the instructions, it's more fun for players to discover them.
Audio design is really good, I assume you wrote the music and made the sound effects yourself?
Fantastic work, I enjoyed this!