In Gomoku, two players alternate placing stones. The first player to make an unbroken line of five stones vertically, horizontally, or diagonally wins. Competitive Renju adds three restrictions for the first player: double-three, double-four, and overline.
Basic rules
Cyber Gomoku is played on a 15x15 board. The first player to line up five stones of their color (CYAN or MAGENTA) vertically, horizontally, or diagonally wins. These fundamentals match traditional Gomoku. The cyber items described later add hidden information and board-changing decisions.
- Board: 15 x 15 squares. Players take turns placing one stone at a time.
- Victory conditions: Arrange five of your stones either vertically, horizontally, or diagonally.
- Draw: If the board is completely filled and there is still no winner, the game will be a draw.
Winning lines and the three forbidden moves
Renju restricts the first player (Black) to reduce the advantage of moving first. Cyber Gomoku applies the same three restrictions to the first player (CYAN). The game blocks a forbidden point before a stone can be placed, so a new player does not need to memorize every pattern. Understanding the restrictions still helps when planning an attack.
- Double-three: One move creates two or more open threes at the same time.
- Double-four: One move creates two or more fours at the same time.
- Overline: One move creates an unbroken line of six or more stones. An overline is not a win for the first player.
The second player (MAGENTA) has none of these restrictions and can win with an overline.
How freestyle Gomoku, Renju, and Cyber Gomoku differ
| Ruleset | Forbidden moves | What happens on a foul |
|---|---|---|
| Freestyle or house-rule Gomoku | May use none | Depends on the agreed rules |
| Competitive Renju | First-player double-three, double-four, and overline | The first player loses |
| Cyber Gomoku | First-player double-three, double-four, and overline | The game blocks the point |
The diagrams show clear introductory patterns. Competitive Renju has finer distinctions: a formation that looks like a three may not count if it cannot legally become a straight four. Consult the Renju rule sources at the end of this page for exact definitions.
Game modes
- Normal mode: Pure Gomoku without items, focused on conventional patterns and calculation.
- Cyber mode: Before the match starts, select one of three cyber items and play. The ability you select is not displayed to your opponent, so when and where you use it is the key to victory.
Both modes can be played in online battles, CPU battles (difficulty levels EASY/NORMAL/HARD), and exhibitions where you can play alternately on the same screen. Rank points are managed independently for each mode (see details Explanation of the rank system).
Cyber item detailed specifications
Each item can be used up to two times per match. Be sure to understand the risks of each, as well as the effects.
1. Stealth Stones — hide your plan
- Effect: On your turn, you can place a "stealth" stone that is invisible to your opponent.
- Number of uses: Up to 2 times per match.
- Display: It appears semi-transparent on your screen and remains invisible on your opponent's screen.
- Detection (important): If your opponent tries to place a stone on the same point, the Stealth Stone is revealed and removed, then the opponent's stone takes the point. You lose the move and one of your two uses.
- Win detection: A five that includes a hidden Stealth Stone still wins. A match can therefore end on a line the opponent could not fully see.
2. Stone Bomb — break the board
- Effect: On your turn, you can place a bomb on the board that is invisible to your opponent. When your opponent (or yourself) steps on the placed square, it will detonate.
- Number of uses: Up to 2 times per match.
- Explosion range: A 3x3 square centered on the detonated square. All Go stones within the range will disappear from the board, regardless of friend or foe.
- Risk: Placing a bomb consumes a turn, and the blast removes your stones too. A poorly placed bomb can destroy your own formation.
3. Stone Radar — search
- Effect: Scan the specified 5x5 square area on the board and discover hidden Stealth Stones and bombs.
- Number of uses: Up to 2 times per match. The scan lasts for 5 turns.
- When discovered: Stealth Stones and bombs discovered by radar become visible to both players from that moment on.
- Risk: The scan finds nothing if your opponent has not used a hidden item. Choosing Radar means betting that there will be something worth finding.
Rules FAQ
How many times can an item be used in one match?
You can use one selected item up to two times per match. Only one item can be selected before the match.
Can you win even with a sequence that includes Stealth Stones?
You can win. Victory will be determined when five are lined up while remaining stealth. Sometimes the battle can be settled with a move that the opponent cannot see.
Will the bomb also erase my stones?
It disappears. All stones within the explosion range (3x3 squares) will be destroyed, regardless of friend or foe. Please consider your formation when choosing the installation location.
When does the prohibition apply?
Applies only to the first move (CYAN). Since moves that are prohibited moves are blocked by the game, you will not be able to make a move by mistake and lose immediately.
Read the beginner strategy guide for practical tactics and the balance-design report for the reasoning behind each item's risk and reward.
Sources and verification
The general Gomoku and Renju explanations refer to public rules from the Renju International Federation and the Japan Renju Federation. Cyber Gomoku-specific behavior was tested by the developer against the public build on August 20, 2026.
- Renju International Federation: International Rules of Renju — formal definitions and match rules
- Japan Renju Federation: About Renju — illustrated overview of the basic rules and forbidden moves
Writing, diagrams, and in-game verification by Gotsuinu. Please use the contact address on the author page to report an error or unclear explanation.
For first-time users, we recommend testing out the behavior of abilities in CPU battles (EASY).