ChessArena is an "io-style" game: real-time, multiplayer and online. It is (at the time of writing) in beta; the description here may be a bit out of date. As a real-time chess variant, it is similar to Kung Fu chess: the pieces slide at a fixed speed through their moves and have so-called a "cooldown" before they can move again. Here, figures can have moves in their queue during their cooldown, and they will make that move immediately after the cooldown ends.
The board is square and quite large and supports several players at once. Players have a limited range of vision around each of their pieces, and the pieces have a limited range of movement. Coins and treasure chests are triggered on empty fields, and players can place rocks and bushes. Coins can be spent on figures and form the basis of the point system; treasure chests contain bombs, rocks or bushes; rocks block movement; the bushes hide the figures inside from the view of the opponent; and the bombs explode after a few seconds, destroying any pieces or terrain within the 3x3 area surrounding them.
Each player enters the game (asynchronously) with a lone king and can control up to four other pieces at any time. Pawns, mounts, hunters and cannons can be bought, while queens must be won through missions or obtained from special tiles; these new figures are dropped on any empty cell adjacent to any player's figure. Capturing or destroying an opponent's king removes that player and all his pieces from the board.
Pieces gain experience by collecting coins or capturing opposing pieces. With enough experience, figures "level up" and gain enhanced abilities: increased field of vision, reduced cooldown time, faster movement, and (except for horses) increased range of movement. Pawns require a bit more explanation. They move without catching orthogonally (in any direction), one two or three places depending on the level of experience. They capture one square diagonally on any level. Pawns move into bushes as if empty, possible capture on orthogonal moves; and a pawn cannot capture diagonally into a bush, even if the player knows that a piece is there. A pawn that starts to capture but finds its target square empty will land there anyway, and a pawn that starts a move without capturing but is found by a figure in its path will be captured.