You certainly know your basics when it comes to platforms (and that is a great thing).  The bats were a bit annoying, but at least it's consistent with bats in ALL platforming games (my own, included).  Bosses were certainly neat, though big puppy was preemptively ending my play-through... a lot...

Anyone else feel like Z & X are backwards for this game, or is it just me?  Well, either way, you did a very fine job and my rating for this game is appropriate for such a comment.  :)

https://www.twitch.tv/videos/2265992076?t=0h37m42s
Here's my live review of the game if you'd like to watch 

Fantastic game, but that third level is bruuuutal

very cute. Some coyote time on jumps would help to make it feel better too.

Nice work overall <3

very fun, but i think it needs more health... it's a struggle having to do everything over and over again

Really well done

Beautiful art direction and presentation overall. Bats are quite tricky to hit, especially in low ceiling corridors. Very nice looking game, congrats!

Very polished art style. I think it’s a bit too difficult that you need to start from the beginning of the level. maybe only restart from the last door? but anyways: well done! subarashi!

I'm not very good at platformers so I had a lot of difficulty progressing through this game. Nonetheless, I enjoyed it! The music is good, and the art is so amazing! Great work on this game!

私、学校で日本語を勉強したから、自分の気持ちを日本語で伝えてみる。
私は横スクロールジャンプアクションゲームに苦手から、このゲームが難しいと思います。それにもかかわらず楽しんだ。音楽が良かったし、絵もすごく良かったし、上出来でした。

Quite a cool game. Loved the sprite work.

You definitely have a recognizable art style when it comes to GB games. Even just from the screenshot I remembered having played some of your previous titles. The bosses and title screens are definitely standouts here.

My  biggest frustration early was with the bat enemy, they were just too high up for my projectile to hit them and would sometimes double injure me upon collision due to the short invincibility window.

Love the Metroidvania style gameplay. There are lots of enemies and bosses and amulets which make it super fun. Fantastic game overall with great music and level design.

Lovely game! Very gameboy-ish indeed. You even made a version for GB, that's amazing!

The bats are such a pain! If you don't run straight past them they can hit you twice too.

Also respawning could be more forgiving, like spawning you at the start of the screen, not the start of the level.

Graphics and sound is top notch, great job on these!

This is fun! Good level design and sprite animation, great environment graphics.
Solid game! Gosh those bats are a pain lol

Wait, you're telling me that in 5 DAYS you solodevved:

• The amazing music, thought that the first tune was Chopin.
• The awesome graphics, everything looks really great, varied, and convincing
• The very good gameplay that seems inspired by Kid Dracula
• The adorable artstyle?

That's nuts! And to top it all off the entire thing is made in GBStudio, feels like it too. Even the logo is intensely GB era.

There are only some minor imperfections. The first one is that it's not immediately obvious what you need to do to prevent the... literal Rondo of Blood chase as a spirit (seriously, wow!) from overtaking you in stage 3. You have to let him overtake you, but in my experience this results in mandatory damage. Additionally, some enemy hitboxes could be a little more generous. The platforms' physics can be slightly confusing at times, too.

It's SO CLOSE to perfection. Please continue this, and make it a cart, give it a digital release, etc. and so on. There's a whole boatload of talent here, and despite the very few complaints this is a straight 10/10 from this Castlevania fan based on the sheer soul on display, and the savant levels of solodevving alone.

Very nice game!

Super cool game. Can't believe this is a game boy file, maybe you should tech me some tricks.

That was quite fun! The gameplay is basic, but highly competent. The art and character design is exceedingly charming! Great work!

I really liked it! The game really captures the Game-Boy soul!

Great game! The gameplay is smooth and fun, the visals and soundtracks are very enjoyable, and the game feels just like an actual GameBoy game.