this was such a cute little metroidvania! you really captured the1-bit gameboy style really well with the art! i like our little piku-niku looking guy, is very cute, as well as all the enemies and bosses especially, really cool stuff! for such limited pixels to work with, the tiles still really do good job at indicating what they do, very nice! the sound effects and music were also very fun and of that era too! i know it would be out place from the inspiration, but having an audio slider for both music and sfx, or just making the overall music a tad bit lower would have been nice, its pretty loud xd.
for the gameplay, it was really fun! the map size is perfect for a jam submission and although i would get lost at some points, i never too lost to the point where it would be frustrating, its very nice! all the power-ups are simple but effectively utilized to its fullest in terms of the navigation of the world! the combat is also fun and the boss fights were pretty tense (some of them i had to cheese in fear of dying though xd). though one thing i wish there was (although its kinda ingrained in games of that era and genre) was that there was better clarity in terms of where potential off-screen threats are. i died a couple of times due to jumping up or falling down onto a platform that so happened was in the direction of those flying block dudes. maybe something like dashed/dotted lines to indicate the existence of those enemies and the extent of their travel range would have been nice (though it could also fail and be mistaken as ground so im not too sure how that would go haha). though if the intention is to emulate some of the difficulty quirks that are found in those games of that era, then all the power to you!
this was a pleasant experience to go through, well done!