from the designer's site:
Arrello is a new game, a cousin of Othello (also known as Reversi).
The game's name is a combination of the words "Arrow" and "Othello". I chose this name because the relationship between the stone you place and the stones you flip is similar to the relationship between an Amazon and an Arrow in the classic abstract game Amazons.
Arrello is a 2-player game played with two-sided stones (green on one side, red on the other), on a 7x7 square grid.
Players take turns, one player playing the stones red side up, the other green side up onto an empty space. If it is placed adjacent to a same-color stone, one can choose to flip a opponent's stone(s).
The game ends when the board is full. The player with the majority of stones in their color wins, because of the odd number of space ties are not possible.