Origin and concept
Game invented by Adam Corbally and others
This chess variant is played by two players on a standard board and pieces, but the board is treated as a four-way battleground towards the center - with natural movement of pawns to always be towards the center battle - hence black hole.
Pieces are setup in corner groups Royalty in the corners with queens diagonal to each other on white and kings diagonal on black. The queen should in the right corner from a players perspective. Each royal faces towards the center of the board, making "in front" be along the diagonal.
In front of each royal is the rook (on the same colour as the royal), then to the royal's right is a bishop, and left is a knight.
Then on each grid edge of that corner 4x4, are pawns.
Royalty, rooks and bishops move as per traditional chess (royalty doesn't move any different when rotated 45, and rooks/bishops simply adopt each other's style when rotated, so for simplicity they maintain their original)
Knights still move "forward two and across one" but now along the diagonal, meaning each knight is now colour-locked, and can move much further - three moves from corner to corner (five in traditional chess). I note that "forward two and one across" on the diagonal is equivalent to an on-grid move of "three and one" (compared to regular chess being "two and one")
Pawns also move forward on the diagonal (two for opening), and always move towards the center according to the quadrant they are in. This is the "black hole" part of blackhole chess, and are also colour-locked except when they attack, which are on traditional grid, and valid in all FOUR directions. This is also the only way a pawn can move away from the center. A pawn that reaches ANY edge on the opponent side of the board (14 total target squares) may be promoted - but it has to battle every damn step of the way to earn it!
There is no "castling" move.
Each royal is flanked by a piece that is colour-locked opposite to the starting piece of that colour.
Pawns gravitate towards the center, leaving stronger pieces to circle as best they can at the edges