Hey, this is pretty well built! This is a pretty solid execution of the theme you were going for.
A few pieces of criticism:
There's not enough CONTRAST in the cave. Now, most would say that it's "too dark" but I don't believe that to be true, as you can make a dark cave easily readable with contrast. Currently the platforms blend together and it's hard to discern what is floor and what is wall.
Here are a few good ways to solve that.
First, use lots of different textures! Usage of a variety of textures allows you to properly guage the 3D space from a distance.
Use different textures for floors than you do on walls. This will allow the player to immediately read where the floor is.
Use lighting in unique ways! In the room with a skylight you have this, as well as the spawn room, where the light shines down on the path forward, you should do this throughout the stage, maybe with torches, or some other light source. Make the main pathway brighter, with it getting darker around the edges.
All of that comes together to create a cavern that is both more visually appealing, and easier to play.
The outdoor segment is actually TOO BRIGHT! With the night sky I think you should knock it down about 20 units in brightness. Regardless, it's pretty and it's readable, so that's not too big of an issue.
Lastly, you said you didn't know what to put in the description, so I can provide you one real quick:
"Cavern-Avern Zone takes place in the caves under Greenflower, trek through flooded caves, traversing precisely over death pits and fighting crawlas"
...Or something like that, admittedly I'm not the best writer.
Take your own creative liberties
With all that out of the way, Welcome to Releases!
