I agree with everything what NewJourneysFire said.
You are trying something different, I really appreciate that, but you need to balance things out better. I also think that the sword does not work well at all in this type of quest. What you should give the player instead is a projectile weapon, like a gun or something, to make for a combat like in Mega Man for example.
I like the graphics and the ideas for the enemies are pretty nice too. I've actually never played Metroid, but now you got me really interested into that game's graphics. I should use them too for a quest sometime xD
Other than that, I really think you should tone down the difficulty. Add more savegame platforms, have an indicator that you can actually save there and have hearts drop more frequently. Most importantly, take away the sword and give out a projectile shooter! After that, add more gimmicks to the areas. Have puzzles and interesting obstacles or add a story. These are just recommendations and I hope you'll consider them at least.
Here's part 1 of my playthrough so far. More videos will come sooner or later! https://www.youtube....h?v=aaGH_1ZLcho
FunshineDX
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Astromeow