Atlantis, by Scip(me), 4-5*

Not a bad level for your first boss fight!

Gameplay: 15.5/20
-Fun: 8/10: The gameplay is a bit fun, but for a 5-star level, I would expect it to be a bit better. The bossfight certainly is attracting in fun levels, but at this point, using 1-speed wave for a boss has become so commonplace at this point that it's become rather generic. The other parts of the level are quite generic as well. I would spice up the gameplay by creating more portals, orbs, jumps, etc. Fun 5-star levels can be created that way.
-Sync: 4/5: You definitely seem to focus on sync, and while there are a few misnomers here and there, it's mostly decently synced. I would still listen to the music a lot more carefully and sync the timings based on the beats.
-Dynamic/Variety: 3.5/5: The dynamic of the gameplay isn't too bad, but I wish that there were more types of gameplay apart from just 0.5x and 1x speed. If you want a 4-5 star level, you'll want a couple of 2x speed thrown in. Using only those two speeds are more typically fashioned to 2-3 star levels, which doesn't seem to be the case here (I believe it to be a 4-star level). Spice the gameplay with more speeds and modes.

Decoration: 15/20
-Block design: 3/5: The block design is quite bland and underdecorated, in my opinion. I notice that you try to use several different types of blocks, but they're so hard to see that it looks like you use just the low-opacity blocks, typical of generic levels. Don't be afraid to use the blocks without lowering the opacity or at least making it look hard to see.
-Background design: 3/5: The background is really limited in variety. I only see 3 total types of background being used. And while some levels can carry this out effectively, given that you don't put much into the background, I would definitely use more background types.
-Air deco: 4.5/5: This is by far your strongest point. There's a lot of glow that fills up the level, preventing it from feeling TOO empty. I definitely would like for you to keep this part up.
-Misc (Boss Design): 4.5/5: For a first boss design, this isn't bad! It's quite well-designed, and though it can definitely look more realistic in many ways, it's quite nice. The variety of the attacks, coupled with the boss-life concept, makes this boss pretty nice.

Originality: 7/10: Again, low variety in the background and block design that seems a lot like copy+paste makes me give this a lower score. There's not much variety in the spikes either (though you use some degree of rotating hazards). Again, put more variety into the whole level! Nothing hurts by experimenting!

Total: 37.5/50 - Decent/Good level (though I'm more leaning on Good).

It's not feature worthy, nor is it rate-worthy, but it's so close! I really love the air deco in the level, as well as most of the sync. I would work on varying the block, background, and hazard decorations. I would also work on creating more portals and speeds to make the gameplay more spicy. For a 4-star level, this is achievable! Just create the right balance for it!

Nice work!