It was a fun neat little throwback and I'd like to see where you take it in the extended edition.
Feedback: Pixel art is great, if you wanted to improve it maybe consider some alternate light sources/tile work and color schemes to differentiate between levels and rooms.
Gameplay wise: We all love progression, whether its starting with a wooden toy sword and proceeding to find the Master Sword or just simplistic feel good improved aesthetics to display your characters progress to correlate with your own improved skills at the game and its mechanics. Perhaps you could implement your own item progression of starting with a small wooden/rusty sword and proceeding to unlock weapons with greater range, or suits of armor where all it changes is the color of the character (maybe some easy to art frills and trim as well) that improves the max life of the character?
Music wise: Great catchy chip tune and effects, but variety is the spice of life.. perhaps short death music, scene change, etc would be in order in a fuller more complete version.
Glitch? wise: The hitbox on the first level mushrooms are a bit janky. The sword both hits them before the animation actually would, and the mushrooms (i let it hit me to test it;) hit you before it looks like they actually touch your character and you would suppose they would as well.
Aside from that nice work and I hope you continue future projects =]