Invented by: N/A
Difference to standard chess: The black and white armies swap starting positions, meaning the Pawns start one step away from promotion. [See below]
This diagram shows a typical opening of Upside-down Chess. As you can see, the Knight is the only piece that can move at the start of the game since all the other's are blocked by the pawns. You'll also notice that the board gets quickly filled with queens, turning the game into an arms race of sorts.
Pawns may only promote to a piece that is taken by the opponent. When no such piece is available, it is forbidden to move the pawn to the last row.