The art and sound is definitely the best part of this game, it's very retro and dated in a charming way. The visual design is very coherent and the sound effects and music sound like an old NES game. It is very enjoyable to view and listen to.
However, the gameplay feels clunky and tight. Even the smallest jumps are unforgiving and feel like I have to get them frame-perfect. The sword slash is also somewhat slow, making it difficult to hit enemies with even if they're simply standing right in front of you. I'm not sure if that's what you were going for, but it feels pretty awful to sit down and play. I would recommend making the jumping floatier and having the sword slash be something more akin to Hollow Knight. If you want to keep the timing aspect of the slash, make it have a long cooldown rather than a long startup.
Overall, it's a game that certainly has potential with its straightforward concept and charming retro presentation, but is weighed down by clunky gameplay. I'm giving this 3 stars, or a 6/10, as I feel like there's much improvement to be made but it's still above average.