Piece Activity

In chess, a piece is considered ‘active’ if it has a lot of options for where to move, and if those options tend to interact with the opponent’s position in meaningful ways. Chess pieces involved in a mating attack, for example, become very active.

The case is similar in Crumble. To be active, a piece must generally be splittable or joinable into pieces that share at least one side with one of the opponent’s pieces — i.e. a piece must be ‘swappable’ into the opponent’s position.

This has several practical implications. For example, when you perform a capture, none of the captured pieces are ‘active’. They can only become active when that region of material is blended with the opponent’s pieces. So, the pieces at the border of that region do generally attempt to be as active as possible, in order to expose the material within.

Likewise, when building a path to victory — i.e. a path to connect a chain of your pieces to all four sides of the board — the impervious parts of that chain will be inactive, even though they are very valuable; while the rest of the chain will be active, as it attempts to render itself either impervious or redundant, and as the opponent attempts to break through at that same spot.

Inactive pieces can render the opponent’s material advantage worthless. If there is a single frontier crossing the board, and White has all the pieces on one side, and Black has all the pieces on the other, then it doesn’t matter whether that frontier cuts off a half, a third, or an eighth of the board. Both sides can only interact along that single frontier, and so both sides have exactly the same amount of active material. Such a situation is often very good for the defender, if they can manage to bring it about.

On the other hand, a very active position can also be good for the defender, because it can render their entire position full of life, and pose many problems for the attacker.

Trying to play a frontier game should only be a last resort. For one thing, it poses only a single problem for the attacker, and if they ever do break through they will win the game. For another, the attacker will generally be on guard against an attempt to create a frontier position, and the defender risks rendering their own game very passive, while still failing to achieve a solid frontier.

On the other hand, if the attacker can maintain an active position while still constructing a solid frontier-like barricade behind them, then the game would have to be considered all but won. The defender would have no way to make winning threats, while the attacker could afford to be as aggressive as possible.