Objective: Checkmate your opponent's King.
 
According to Greek mythology, the Hydra was a beast with seven heads. Whenever someone cut off one of the heads, it quickly grew back. If you capture one of your opponent's pieces in Hydra Chess, your opponent may reinsert it, but it will change into a piece of less value: Pawn < Knight < Bishop < Rook < Queen. Hence Pawns are lost immediately and do now grow back.
 
To reinstate a piece, just click an empty square of the board.
 
In the default variant, up to sixteen captured pieces can be stored.
In the Swap Variant, only one captured piece will be stored.
 
 
More freeware as well as real puzzles and games under http://karl.kiwi.gen.nz.