Tip: You can use Lunar Magic's Overworld Layer 3 Editing system to edit or create your own layer 3 images (castle bricks, fish, rocks) and apply unique effects per level via the Layer 3 Bypass in the main editor.
The design is well managed. Sometimes it felt repetitive, like, you have to do the same things in multiple levels (like finding a springboard and using it to jump over an obstacle), but it was okay. Some parts were also a bit too empty, like in the castle, in the beginning of the room where the midway point is. Not much more to say about this hack, since it's a pretty traditional one mostly.
Aesthetics also follow what a traditional vanilla hack is. No shenanigans with Map16, nor custom palettes. Just pure vanilla.
Overall, it was okay. A tad repetitive, but it works for some fun. 3/5.