Chess Marathon Achievement
You get this secret achievement by playing a game of rapid, blitz, or bullet chess that lasts for more than 100 moves. You get the achievement regardless of whether you win, lose or draw. You can get the achievement in both rated and unrated games.
You can get this achievement by playing a friend unrated with you both working together to get the achievement, or you can try to achieve it in a rated game against a random opponent. Either way, you will need to be wary of the 50 move rule. The game will be counted as a draw if 50 moves are played by each player without a capture or pawn move occurring. If, sometime after the 50th move of the game, a pawn move or capture is played, you will not have to worry about this, as the draw will occur after move 100.
IMPORTANT: Variants do not count for this achievement
