Really cool little Zelda-y Metroidvania!
I really liked the art, and the sfx, music and combat were all really good!
The boss fight felt very Undertale and was quite intense which I liked, although I think I could've just left the island without beating it... Not 100% sure, but it spawns you before the bridge bit and you have the AMVE. Also although the boss was really cool, some of its moves in certain combinations lead to pretty much unavoidable hits, mainly nearer the end of the fight.
I do kind of agree with some of the other comments that there could've been more variety in the upgrades, but I thought the dash was really well done, maybe like a fire wand or hookshot or something.
Overall I really enjoyed it, well done!