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Gomoku looks innocent - drop a stone, line up five, done - but on Classic Play Games' 15x15 board it quickly becomes a duel of threats and counter-threats. Black moves first, usually onto the center point, and from there every stone either builds toward your own five or smothers your opponent's. There are no captures, no dice, and no territory to count: the win is purely a race to forge an unbroken line of five before the other side does, while reading two or three moves ahead.
How to Play Gomoku
Gomoku is played on a 15x15 grid by two players, Black and White. Black always moves first. On your turn you place one stone on any empty intersection; once placed, stones never move and are never captured. Play alternates until someone wins or the board fills. This version is free-style Gomoku - no opening restrictions, no swap rule, and no forbidden moves - so Black keeps a genuine first-move advantage. When you play against the computer you are always Black and the AI is always White, so you get that first move.
You win the instant you form an unbroken line of five of your own stones horizontally, vertically, or diagonally. A line of six or more (an overline) also counts as a win here - it is not forbidden - so a run of five anywhere inside a longer chain still ends the game in your favor. If all 225 intersections are filled and neither side has made five, the game is scored as a draw, though draws are rare on a board this size.
Against the computer you pick one of three levels before starting. Easy searches only two plies deep and plays a purely random move about 30 percent of the time, so it routinely leaves open threes and forks standing. Medium looks roughly four plies ahead and blunders randomly only about 5 percent of the time. Hard searches six plies deep and never plays a random move. One thing every level always does first, before any search or blunder roll: it takes an immediate winning move, and it blocks a spot where you would otherwise complete five on your next turn. The catch is that this guard only patches a single five-completion - it cannot stop an open four, which threatens five at both ends. Local two-player mode shares one device and alternates turns.
Open Fours, Double Threats, and Beating the Block
The single most important pattern in Gomoku is the open three - three of your stones in a row with empty space on both ends. Left alone it becomes an open four (four in a row with both ends open), and an open four simply wins: the opponent can only plug one end, and you complete five on the other. The engine's evaluation reflects this exactly - it scores an open four at 50000, ten times the 5000 it gives an open three or a closed (one-end) four - which is why a searching AI will drop almost anything to stop your three before it matures into that open four.
This is the key to beating the computer. The AI's mandatory guard only blocks a single immediate five-completion, so it cannot stop an open four (two completion points) - if you ever get a clean _XXXX_, you have already won, even against Hard. When the opponent is sharp enough to kill your open threes before they reach an open four, fall back on the double threat: one move that creates two separate four-threats at once (a double-four, or a four combined with an open three). The opponent answers only one and you finish the other. The classic builders are the double-three fork and the broken three (a gap like X_XX) that defenders often overlook.
Center control matters more than it looks. Against the AI you open the game, and the center point H8 is the strongest first stone because it touches the most potential five-lines. The AI (at any level) answers a center stone with the adjacent diagonal G7 - this reply is hardwired, not a sign of deep thinking - and from there the fight is over the middle. The engine also adds a small center bonus to its scoring, so stones drifting toward the edges are worth less; keep your build near the center and force the AI to react to you.
On defense, learn to tell a live threat from a dead one. A three or four that is blocked on both ends can never become five and is safe to ignore - spend that move building your own attack. When you must defend, block at the end that also extends one of your own lines so a single stone does double duty. And never let the opponent reach an open four or a fork unanswered: the AI's evaluation and lookahead are exactly what stop you from doing the same, so the deeper Medium and especially Hard will punish a missed open three of theirs immediately.
Frequently Asked Questions
Does six in a row (an overline) count as a win in this Gomoku?
Yes. This is free-style Gomoku, so any unbroken line of five or more of your stones wins - six, seven, or longer all count. Some tournament rule sets forbid overlines for Black, but that restriction is not used here, so you never have to worry about accidentally overshooting five.
Is there a swap rule or any restriction on Black's opening?
No. There is no swap, no pie rule, and no forbidden first moves. Black opens on any intersection and play proceeds freely. When you play the computer you are always Black, so you automatically get the first-move advantage - most players open on the center point H8, and the AI then replies on the diagonal G7.
Can the AI ever let my five-in-a-row through?
Every level always takes an immediate win and always blocks a single spot where you would complete five next turn - so a plain closed four (one open end) gets stopped every time. But that guard only patches one completion point, so an open four, with five available at both ends, beats every level including Hard. The reliable ways to win are an open four or a double threat the AI can only half-answer.
What actually changes between Easy, Medium, and Hard?
Two things: search depth and randomness. Easy searches two plies and plays a fully random move about 30 percent of the time, so it leaves open threes and forks standing. Medium searches four plies and blunders randomly about 5 percent of the time. Hard searches six plies and never plays a random move, so it reliably kills your open threes before they become open fours. All three still take immediate wins and block immediate fives regardless of level.
Why does the computer always answer my center stone in the same spot?
Because that reply is hardcoded. If you open on the center (H8), the AI plays the adjacent diagonal G7 every time, at any difficulty, before it does any searching at all. After that fixed second move it switches to real evaluation, which adds a center bonus so middle stones are scored higher - which is why strong play, human or AI, gravitates toward the center.