Super X Chess Windows, Mac, Linux game

Hello! I made this chess game: Store.steampowered.com and now I'm explaining my reasonings behind the design decisions of the game. Open to get to know what you think, too.

The basic premise seems solid as your using your turn (time) for creating more powerful pieces, so there is already a tradeoff there, because your really not developing your piece's position to a better one while doing that. Also your having less pieces after combining your pieces, so that can also be a tradeoff, as when you have less pieces, your lowering your ability to attack the same square as many times as with more pieces.

I feel like the movement logics for the piece combinations of same pieces (Pawn+Pawn, Rook+Rook, Knight+Knight) are solid, too. But those were the difficult part of the design. I tried to get the Knight+Knight to be approximately as strong piece as Bishop+Knight piece and feel like I managed to do it. Rook+Rook piece I tried to get stronger than the other pieces, but not overpowered. Also it is important that the pieces keep some weaknesses, so Knight+Knight still can't attack any adjacent squares and Rook+Rook can be weak if not in open position.

Maybe more controversial was that I decided to drop the normal pawn ability to promote to Queen. I felt like it's more interesting, because then you get a new piece which still could combine again and also it's more interesting decision to think to what piece to promote. Before it was 99% chance for the piece to promote to Queen, now it's maybe something like 80% to Rook, 10% to bishop and 10% to Knight depending on what situation needs. It's also a small nerf for regular pawns to encourage players more to promote their pawns.