How to Play Gomoku (Cờ Ca-rô) — Beginner's Guide

The Goal

Connect five of your marks in a row — horizontally, vertically, or diagonally — before your opponent does. You play X, the computer plays O, and X always moves first.

The Board

Gomoku is played on the intersections of a grid, like a page of Vietnamese school notebook paper (giấy ô ly). In this app you can choose three board sizes:

• 10×10 — quick games, great for learning
• 15×15 — the classic size (default)
• 20×20 — long, strategic battles

On each turn you place one mark on any empty intersection. There are no captures and no movement — a mark stays where it was placed for the whole game.

The Vietnamese Rules — Two Twists

This app plays the rules used across Vietnam, which differ from Japanese renju:

• Exactly five blocked at BOTH ends does NOT win. If your line of exactly five has an opponent's mark (or the edge of the board) immediately at both ends, it is a "dead five" and the game continues. One open end is enough — that five wins.
• Six or more ALWAYS wins. An "overline" of 6, 7, or more connected marks wins immediately, even if both ends are blocked.
• No forbidden moves. Unlike renju, there are no banned double-threes or double-fours — every placement is legal.
• Draw: if the board fills completely with no winning line, the game is a draw.

Basic Strategy

• Take the center. The center intersection touches the most possible lines — the strongest first move.
• Open threes are threats. Three in a row with both ends empty ("open three") becomes an open four next move, and an open four cannot be stopped: block one end and your opponent plays the other.
• Block fours immediately. When the opponent has four in a row, count the open ends. One open end: you must play there now. Two open ends: only winning first can save you.
• The double-three (3–3) is the classic killer. One move that creates two open threes at once can only be half-blocked — the other three grows into an open four. Look for crossing cells where a row and a column both need the same intersection.
• Mind the blocked-ends rule. Before celebrating a five, check both ends. And when defending, remember a five can be killed in advance by sealing its far end early.

In This App

• Play against the computer at 12 difficulty levels, with real swap-sides and hint buttons.
• Rooms let you play friends in real time — the host picks the board size — with private room chat, voice chat, and spectators.
• Correspondence games for playing at your own pace, a daily puzzle, community-created puzzles, a tactics library, Elo ratings, quests, and push notifications — all in Vietnamese and English.