Connect Four Glossary
Strategy terms and concepts explained. From basic threats to advanced endgame theory.
Threats
Double Threat
A double threat is a position where you have two ways to complete four in a row on your next move, making it impossible for your opponent to block both.
Vertical Threat
A vertical threat occurs when you have three pieces stacked in a column with at least one empty space directly above, threatening to complete four in a row.
Horizontal Threat
A horizontal threat is a line of three pieces in a row along a single row, threatening to extend to four if an adjacent space is playable.
Diagonal Threat
A diagonal threat is a line of three pieces along a diagonal (ascending or descending), threatening to complete four in a row with one more piece.
Strategy
Center Control
Center control means prioritizing the middle column (column 4) because pieces placed there connect to more potential winning lines than pieces on the edges.
Odd-Even Strategy
The odd-even strategy exploits the fact that player 1 makes moves on odd turns and player 2 on even turns, so threats on odd rows naturally favor player 1 and threats on even rows favor player 2.
Tempo
Tempo refers to the initiative or pace of play. A player with tempo is making threats that force the opponent to respond defensively rather than pursue their own plans.
Trap
A trap is a deceptive position where the opponent appears safe but is actually walking into a forced loss, often through a hidden double threat.
Concepts
Zugzwang
Zugzwang is a position where the player whose turn it is would prefer to pass, because every available move worsens their position or leads to a loss.
J-Configuration
The J-configuration is a specific arrangement of three pieces forming a J or L shape that, when completed with a fourth piece, creates two simultaneous threats.
Figure Seven Trap
The figure seven trap is a configuration where three pieces form the shape of the number 7, creating a structure that generates two winning threats from a single setup.
Forced Win
A forced win is a board position where one player can guarantee victory no matter how the opponent responds, meaning every possible line of play leads to a win.
Perfect Play
Perfect play means making the optimal move in every position. Connect Four was solved in 1988, proving that the first player wins with perfect play starting from the center column.
Competitive
Rating System
The rating system uses Glicko-2 to measure player skill. Everyone starts at 1500, and your rating goes up when you beat stronger opponents and down when you lose to weaker ones.
Endgame
The endgame is the final phase of a Connect Four game when the board is mostly full, choices are limited, and the outcome is often determined by threat placement and row parity.