Ribbon Ring Stage Analysis

Hey! Just got my copy of the game, and decided to dig into how exactly Ribbon Ring operates. There is an RNG component, and there are quite a few mysteries regarding the stage to me still, but here's what I know:

• Ribbon Ring's base form is a flat, 10x10 square.
• After a few seconds, it transforms. The first transformation, as far as I know, is always a 4x4 square that rises in the middle of the stage. I call this "A." Image
• After a few seconds on A, the stage transforms again. This is the only instance in which the stage transforms without player involvement (destruction of the blocks.) I call this "B." Image
• After B is destroyed, it is randomly replaced with one of the following:
• A pair of vertically (relative to spawn points) oriented 4x4s connecting with one another. I call this "C." Image
• A pair of horizontally oriented 3x3s on both sides of the grid. I call this "D." Image
• A pair of vertically oriented 3x3 on both sides of the grid. I call this "E." Image

I'm sure there are a lot of things I've missed; because there are so many variables when it comes to destroying the blocks, I opted only to cover transformations appearing after destroying every block. I'm sure I missed some that appear after destroying every block, too. I suspect the existence of an "F," which acts as a horizontal equivalent to C, as D and E do to one another.

If you know anything more, or if there's anything I got wrong, please tell me!

Edit 1: I've come across a new transformation. It's a cross shape, all the way vertically and horizontally. I've seen both 2-wide and 1-wide.

Edit 2: Another new transformation! This one is a square border all around, with blocks on top of every other block, making it resemble a fortress of some sort.