Great! Just played it again. I liked the new additions, which makes it more challenging. Is there a fixed mutation sequence? It seems that the blocks can only mutate a limited number of times before stopping.
Previously I noticed that the following block got stuck on the top right hand edge when rotating, but thought it was me pressing the wrong buttons. It was originally upright before I pressed rotate:
Also, maybe you might want to reconsider the rotated positions of the T-shaped piece.
During the gameplay just now, an orange I-shaped piece which showed up on "Next Piece" once changed to a blue or green L-shaped piece when it comes out from the top. I'm quite sure I didn't press the mutate key, and I'm not sure why, maybe something triggered the mutation sequence?