Hexagonal - Chess Variants

Hexagonal chess refers to a group of chess variants played on boards composed of hexagon cells. The best known is Gliński's variant, played on a symmetric 91-cell hexagonal board.

Since each hexagonal cell not on a board edge has six neighbor cells, there is increased mobility for pieces compared to a standard orthogonal chessboard. (E.g., a rook has six natural directions for movement instead of four.) Three colours are typically used so that no two neighboring cells are the same colour, and a colour-restricted game piece such as the orthodox chess bishop usually comes in sets of three per player in order to maintain the game's balance.
I'm trying to create an application that allows a player of any level to enjoy the game.

Play Hexa Chess, unlock levels and be Chess Master!

Chess pieces:
Endgame studies
These endgame studies apply to both Gliński's and McCooey's variants

king + two knights can checkmate a lone king;
king + rook beats king + knight (no fortress draws and a negligible number (0.0019%) of perpetual check draws);
king + rook beats king + bishop (no fortress draws and no perpetual check draws);
king + two bishops cannot checkmate a lone king, except for some very rare positions (0.17%);
king + knight + bishop cannot checkmate a lone king, except for some very rare positions (0.5%);
king + queen does not beat king + rook: 4.3% of the positions are perpetual check draws, and 37.2% are fortress draws;
king + rook can checkmate a lone king.
Important Chess situations:

- Check - the situation in chess when a king is under immediate attack by opponent's pieces
- Checkmate - the situation in chess when the player whose turn it is to move is in check and has no legal move to escape check.
- Stalemate - the situation in chess when the player whose turn it is to move has no legal move and is not in check. (draw)

The goal of the game is to checkmate the other king.

Two special moves in Chess:

- Castling is a double move, performed by the king and the rook that never moved.
- En passant is a move in which a pawn can take an opponent's pawn if it jumps over a field under the pawn's blow.

Features:

- Four levels of difficulty
- Chess Puzzles
- Game Assistant (Helper)
- Ability to undo a move
- Hints of moves
- Stars for levels completed without the undo button
- Seven different themes
- Two board views (Vertical - 2D and Horizontal - 3D)
- Alternate mode
- 2 player mode
- Realistic graphics
- Save function
- Sound effects
- Small size

If you want to play good Hexa Chess, you can help me make the app better.
Please write your feedback and suggestions here; I will read them and improve the quality of the application!