Go – from the Japanese word igo, meaning “encircling game” – is a strategy board game that originated in China approximately 3500 years ago. The game starts with an empty grid set on a wooden board. Players then take turns to place black and white stones on the intersections of the crossing lines. The objective of each player is to capture the stones of the opponent. A stone – or chain of connected stones – is captured if all its four degrees of freedom (the four surrounding intersections) are occupied by an opponent's stones. Despite these simple rules, go is a game of extraordinary complexity and beauty. A player in any typical game among experts has an average of a few hundred choices per move, making strategies strongly tied to intuition, experience, and pattern recognition. The players' skills strengthen by learning to identify a certain balance between the territory they give away and the force they exert on the opponent. It is a gentle-strategy game.

The lack of skillfulness typically results in pushing the opponent's beads instead of encircling them. Successful encircling calls for a delicate, wise balance between force and territory, limiting and yielding, pushing and letting go. A suitable way to go: attack from the corners. Continue along the sides. Move into the center. Trap. The goal is to constrain the freedom of the opponent applying the minimum amount of force.

In Nature, a similar balance sustains the glide of a seagull on a current of air. The form of the wings separates the flow of air molecules so that moving air molecules passing underneath exert a lifting force larger than the downward pressure of those passing above. The resulting force is just enough to compensate gravity and keep the bird in a comfortable flight.

In spirit, a similar balance is the principle behind optical trapping. Photons can exert tiny – but observable – forces by exchanging momentum with very small particles. Without a good strategy, though, photons can only push.