Connect 4 Online is a 2 player board game similar to Tic-Tac-Toe. Each player takes turns dropping a colored disc into a board that has 7 vertical columns and 6 horizontal rows. The goal of the game is to connect four pieces of the same color–vertically, horizontally, or diagonally–before the other player does so.
Connect 4 game ends in a tie if neither player connects four when all the 42 board positions are filled up. The first player begins by dropping his/her yellow disc into the center column of the game board. The two players then alternate turns dropping one of their discs at a time into an unfilled column, until the second player, with red discs, achieves four discs in a row, diagonally, and wins.
Connect 4 Gameplay
Mathematical solution
Connect 4 is a two-player game with perfect information for both sides. This term describes games where one player at a time plays, players have all the information about moves that have taken place and all moves that can take place, for a given game state. Connect 4 also belongs to the classification of an adversarial, zero-sum game, since a player’s advantage is an opponent’s disadvantage.
One measure of complexity of the Connect 4 game is the number of possible games board positions. For classic Connect 4 played on 6 high, 7 wide grid, there are 4,531,985,219,092 positions for all game boards populated with 0 to 42 pieces.
The game was first solved by James Dow Allen (October 1, 1988), and independently by Victor Allis (October 16, 1988). Allis describes a knowledge-based approach, with nine strategies, as a solution for Connect 4. Allen also describes winning strategies in his analysis of the game. At the time of the initial solutions for Connect 4, brute-force analysis was not deemed feasible given the game’s complexity and the computer technology available at the time.
Connect 4 has since been solved with brute-force methods, beginning with John Tromp’s work in compiling an 8-ply database (February 4, 1995). The artificial intelligence algorithms able to strongly solve Connect 4 are minimax or negamax, with optimizations that include alpha-beta pruning, move ordering, and transposition tables. The code for solving Connect 4 with these methods is also the basis for the Fhourstones integer performance benchmark.
The solved conclusion for Connect 4 is first-player-win. With perfect play, the first player can force a win, on or before the 41st move by starting in the middle column. The game is a theoretical draw when the first player starts in the columns adjacent to the center. For the edges of the game board, column 1 and 2 on left (or column 7 and 6 on right), the exact move-value score for first player start is loss on the 40th move, and loss on the 42nd move, respectively. In other words, by starting with the four outer columns, the first player allows the second player to force a win.
Rule variations
There are many variations of Connect 4 with differing game board sizes, game pieces, and gameplay rules. Many variations are popular with game theory and artificial intelligence research, rather than with physical game boards and gameplay by persons.
The most commonly-used Connect 4 board size is 7 columns × 6 rows. Size variations include 5×4, 6×5, 8×7, 9×7, 10×7, 8×8, Infinite Connect-Four, and Cylinder-Infinite Connect-Four.
Several versions of Hasbro’s Connect 4 physical gameboard make it easy to remove game pieces from the bottom one at a time. Along with traditional gameplay, this feature allows for variations of the game. Some earlier game versions also included specially-marked discs, and cardboard column extenders, for additional variations to the game.
PopOut
PopOut starts the same as traditional gameplay, with an empty board and players alternating turns placing their own colored discs into the board. During each turn, a player can either add another disc from the top, or if one has any discs of their own color on the bottom row, remove (or “pop out”) a disc of one’s own color from the bottom. Popping a disc out from the bottom drops every disc above it down one space, changing their relationship with the rest of the board and changing the possibilities for a connection. The first player to Connect 4 of their discs horizontally, vertically, or diagonally wins the game.
Pop 10
Before play begins, Pop 10 is set up differently from the traditional game. Taking turns, each player places one of their own color discs into the slots filling up only the bottom row, then moving on to the next row until it is filled, and so forth until all rows have been filled.
Gameplay works by players taking turns removing a disc of one’s own color through the bottom of the board. If the disc that was removed was part of a four-disc connection at the time of its removal, the player sets it aside out of play and immediately takes another turn. If it was not part of a “Connect 4”, then it must be placed back on the board through a slot at the top into any open space in an alternate column (whenever possible) and the turn ends, switching to the other player. The first player to set aside ten discs of their color wins the game.
Five-in-a-Row
The Five-in-a-Row variation for Connect 4 is a game played on a 6 high, 9 wide, grid. Two additional board columns, already filled with player pieces in an alternating pattern, are added to the left and right sides of the standard 6-by-7 game board. The game plays similarly to the original Connect 4, except players must now get five pieces in a row to win. This is still a 42-ply game since the two new columns added to the game represent twelve game pieces already played, before the start of a game.
Power Up
In this variation of Connect 4, players begin a game with one or more specially-marked “Power Checkers” game pieces, which each player may choose to play once per game. When playing a piece marked with an anvil icon, for example, the player may immediately pop out all pieces below it, leaving the anvil piece at the bottom row of the game board. Other marked game pieces include one with a wall icon, allowing a player to play a second consecutive non-winning turn with an unmarked piece; a “×2” icon, allowing for an unrestricted second turn with an unmarked piece; and a bomb icon, allowing a player to immediately pop out an opponent’s piece.
Frequently Asked Questions (FAQs)
Is there a strategy to connect 4?
One basic strategy for Connect four is to have disks in the middle, because this opens up the most opportunities for you to make connections. Because there are an odd number of columns, having disks in the middle means you can make connections in any direction.
How do you win connect 4 every time?
1. Anticipate Your Opponent’s Moves. The game is indeed very similar to other strategy games, but for players who are not used to the rack, it can be almost intimidating. …
2. Stay in the Middle. …
3. Look Ahead. …
4. Watch out for Game-Ending Spaces.
Has Connect 4 been solved?
Connect Four has since been solved with brute-force methods, beginning with John Tromp’s work in compiling an 8-ply database (February 4, 1995).
What are the rules of Connect 4?
The two players then alternate turns dropping one of their discs at a time into an unfilled column, until the second player, with red discs, achieves a diagonal four in a row, and wins the game. If the board fills up before either player achieves four in a row, then the game is a draw.
