Every stone (and connected group of stones of the same color) must have at least one liberty — an empty adjacent intersection (up, down, left, right — never diagonal). If a stone or group has no liberties, it is captured and removed from the board.

• A stone in the middle of an empty board has 4 liberties.
• A stone on the edge has 3 liberties.
• A stone in a corner has 2 liberties.
• When two or more same-colored stones are adjacent, they form a group and share all their liberties collectively.

You capture opponent stones by completely surrounding them — filling all their liberties. The captured stones are immediately removed from the board and kept as prisoners. Each prisoner is worth one point at the end of the game (Japanese scoring).

You may place a stone that initially appears to have no liberties, provided that the placement itself captures opponent stones first — giving your new stone freedom.

Go has one special rule to prevent infinite loops: the Ko rule. After any move, the board position may not return to a state it was in on a previous turn.

The most common application: if capturing a single stone would recreate the board position from your opponent's previous move, you may not make that capture immediately. You must play elsewhere first (a "ko threat"), and only then recapture if the ko is still available.

• Simple Ko: A single-stone fight that alternates. You must play elsewhere before recapturing.
• Triple Ko: A rare situation where three ko fights occur simultaneously — in many rulesets this results in a void game.
• Eternal Life: Extremely rare board shapes that loop — resolved by special rules.

A group is considered alive if it cannot be captured, and dead if it inevitably will be captured, even with best play. The key concept is eyes.

An eye is an empty intersection completely surrounded by your stones such that the opponent cannot legally fill it without capturing their own stone (self-capture rule). A group with two or more eyes can never be captured — it is unconditionally alive.

• One eye: Not safe — the opponent can eventually fill surrounding liberties and capture the group.
• Two eyes: Unconditionally alive. The opponent can never fill both eyes simultaneously.
• False eye: An intersection that looks like an eye but can be filled — groups relying on false eyes may be dead.

When both players agree that no more useful moves exist — all territories are settled, all dead stones have been identified — they each pass in turn. In this game, each player has exactly one pass. When both have passed, the game ends and scoring begins.

If there is disagreement about which stones are dead, players must play out the disputed areas. You may also resign at any time if you feel your position is unwinnable.

The opening phase (fuseki — "laying out stones") involves establishing frameworks and claiming portions of the board before the fighting begins. At the professional level, fuseki has been studied for centuries and comprises thousands of known patterns.

• 4-4 Point (hoshi): The most popular modern opening. Played on the star point, it sacrifices some corner territory for strong influence toward the center.
• 3-4 Point (komoku): Traditional and solid. Claims more corner territory while remaining flexible for various development patterns.
• 3-3 Point (san-san): Secures the corner completely but gives up all outside influence. Often used as an invasion point later in the game.
• 5-3 / 5-4 Points: More aggressive and situational openings.
• Tengen (center): The center star point — a bold, influence-oriented opening rarely used by professionals except as a bold statement.

The middle game (chuban) is where the board transforms from frameworks into concrete battles. Key concepts:

• Invasion: Entering an opponent's framework before it solidifies into territory. Timing is critical — too early and you have insufficient support; too late and the territory is too thick to invade.
• Reduction: Playing at the edge of an opponent's moyo (potential territory) to shrink it without fully invading. Safer than invasion.
• Sente and gote: A sente move forces your opponent to respond (initiative). A gote move does not. Maintaining sente is hugely advantageous.
• Aji: Latent potential. A position that looks settled but contains hidden follow-up threats is said to have good aji.
• Thickness: A group of stones that is clearly alive, has no weaknesses, and exerts powerful influence on surrounding areas.

The endgame (yose) is where boundaries are finalized and last points are counted. Though it seems mechanical compared to middle-game fighting, endgame is a precise skill that can swing games by 10+ points.

• Moves in the endgame have specific point values — always play the largest remaining endgame move.
• Sente endgame moves (forcing a response) are worth roughly twice their face value — play them first.
• Ko fights often occur in the endgame when both players have accumulated ko threats.
• A mistake of even 1–2 points in the endgame can flip the outcome of a close game.

One of Go's deepest strategic tensions is between territory (solid, enclosed points) and influence (outward-facing thickness with future potential). Both are valid paths to winning.

• Territorial style: Secures concrete points immediately. Plays on the third line. Leaves less to chance.
• Influence style: Builds walls and frameworks (moyo) that may become massive territory if the opponent invades unsuccessfully. Higher risk, higher reward.
• The strongest players adapt their style to the demands of each specific position rather than committing to one approach.

• Influence map / Moyo: A large framework of loosely placed stones that threatens to enclose massive territory. The opponent must invade or reduce — the question is when and where.
• Thickness: A solidly connected, living group with no weaknesses. Thick groups radiate influence across the board. Never invade thick positions — reduce from a distance.
• Shape: The spatial arrangement of your stones. Good shape is efficient (each stone doing multiple jobs). Bad shape is inefficient — "empty triangles" and "dumpling shapes" waste potential.
• Aji (味): Lingering flavor. A position or stone that looks settled but contains hidden follow-up threats. Good players preserve and exploit aji rather than resolving it prematurely.
• Tenuki: Ignoring your opponent's local threat and playing elsewhere. Powerful when the local threat is small and the global opportunity is large.
• Kikashi: A forcing move that extracts a concession before playing elsewhere. The opponent is compelled to respond, and the move is not wasted even if you tenuki afterward.
• Miai: Two equivalent points such that if your opponent takes one, you take the other. Recognizing miai allows you to remain untroubled by apparent threats.

• Fuseki (布石): The opening phase. Stones placed in the early game shape the entire contest. Focus on corners first (easiest to secure), then sides, then center.
• Joseki (定石): Established corner sequences where both players play optimally. Hundreds of joseki exist; learning a few key ones dramatically improves corner fights.
• Sente / Gote: Sente means "initiative" — your move forces the opponent to respond, keeping your momentum. Gote means you respond to them. In the endgame, sente moves are worth nearly double a gote move of the same size.
• Vital Point: The single most important intersection in a local fight — often the point that either kills the opponent's group or saves yours. Reading to find vital points is the core of tsumego training.
• Direction of Play: When attacking, drive the opponent toward your thickness and away from safety. When building territory, extend toward the open board. "Make your opponent run into walls."
• Count the Board: Periodically estimate the score. If ahead, play solidly and avoid unnecessary fights (reduce, don't invade). If behind, create chaos — ko fights, invasions, complex sequences where mistakes are possible.
• The Third Line vs. Fourth Line: The third line (3 intersections from the edge) builds secure territory. The fourth line builds influence. Strong players balance both throughout the game.
• Big Points vs. Local Urgency: The hardest judgment in Go — is the global big point more valuable than responding to a local threat? Recognizing true urgency separates dan players from kyu players.

This is a full-featured Go client built entirely in the browser. It includes a living sky ambience system, AI-powered commentary, real-time analysis, famous game replays, tsumego puzzles, and much more. Here is a complete guide to every feature.

• Mode: Play vs Bot (single player against AI) or vs Human (two players on the same screen, passing the device).
• Bot Difficulty: Four levels — Wanderer (random), Apprentice (heuristic), Master (Monte Carlo search), Grandmaster (UCB1 MCTS with deep rollouts). Grandmaster is genuinely very hard to beat.
• Your Color: Play as Black (goes first, disadvantage) or White (komi compensation).
• Board Size: 9×9 (quick, beginner-friendly), 13×13 (intermediate), 19×19 (full game, ~1–3 hours).
• Komi: White's compensation bonus. Standard is 6.5 (Japanese rules). Set to 0 for handicap games.
• Time Control: Optional move timer — 30s, 60s, or 2 minutes per move. Runs out → Byo-Yomi kicks in: 3 extra 30-second periods before time loss.
• Board Theme: Five visual themes: Classic Wood, Cyber Neon, Jade Imperial, Cherry Blossom, Obsidian. Each theme changes board, stone, and UI colors.
• Handicap Stones: Give Black a starting advantage of 2–9 pre-placed stones. Automatically positions stones on traditional star points.
• Bot Opening Book: When enabled (Level 3–4), the bot plays professional fuseki patterns for the first few moves rather than calculating from scratch.
• Load SGF: Import a .sgf game record file to review any game in the replay viewer.

• Coordinate Labels: Toggle A–T letter labels and 1–19 number labels along the board edges. Click Coords in the toolbar.
• Last Move Marker: A small circle appears on the most recently placed stone so you never lose track of where your opponent played.
• Ghost Stone Preview: As you hover over the board, a semi-transparent preview stone shows where you would play.
• Board Texture: Upload your own image as a board background (PNG/JPG/WebP), or choose from preset textures including light wood, dark rosewood, slate, and bamboo mat. Accessible via Texture button.
• Theme Switcher: The five dots in the right panel switch visual themes instantly, even mid-game.
• Stone Trail Particles: Each placed stone spawns particle effects that fade away — toggle with the Trail button.
• Capture Animation: Captured stones fly in a parabolic arc toward the prisoner bowl, with a pulsed flash on the board and pitched sound. The prisoner counter pulses when stones land.
• Ko Pulse: When a Ko fight is active, the relevant stone pulses visually on the board to draw your attention.
• Handicap Badge: A small dot on the board stones shows which are handicap stones.
• Annotation Mode: Toggle Annotate to draw symbols (circles, triangles, squares, X marks) on the board for analysis. Arrows can also be drawn. All annotations are cleared on new game.
• Territory Overlay: After both players pass, toggle Territory to see shaded regions showing estimated territory for each player.
• Dead Stone Marking: After game end, click Mark Dead then click stones to mark them as dead for scoring purposes. Click Score to finalize.

• AI Live Commentary: Toggle the Commentary button. After each move, a live AI commentator (powered by Claude) provides 2–3 sentences of authentic Go broadcast commentary, including move coordinates, phase, and captures. Falls back to template commentary if offline. Your moves' commentary stays visible for at least 4 seconds before the bot's commentary appears.
• Influence Heat Map: Toggle Heat Map to see a color overlay showing which intersections each player influences. Blue = Black's influence, Red = White's influence. Intensity reflects strength. Computed fresh each turn via BFS from every stone.
• AI Hint: Press Hint to ask the AI for a suggested move. The hint glows on the board for 8 seconds with an explanation (captures, atari relief, territory). Uses MCTS analysis at your current difficulty level.
• Move Explanation Box: Automatically shown after each bot move — explains what the bot played and why (captures, atari, territory building, etc.).
• Post-Game AI Analysis: After a game ends, click 🔍 AI Analysis on the win screen. Claude analyzes your game and returns a letter grade, playing style assessment, 3 best moves, 3 key mistakes, the turning point, and a coaching tip — all as a structured card.
• Joseki Guide Overlay: Toggle Joseki in the right panel during the opening phase (first 12 moves). Golden stars highlight recommended 4-4 and 3-4 corner points; blue diamonds suggest star-point extensions once corners are claimed.
• Complexity Meter: Toggle Complexity to open a gauge showing the current position's tactical tension — accounting for groups in atari, active ko fights, unsettled groups, and total captures. Ranges from Calm to Volcanic 🌋.

• Tsumego Puzzle Mode: Access via Tsumego button. A library of 20 life-and-death problems of varying difficulty (Easy/Medium/Hard), each with a hint system, star rating, and progress tracker. Click a point on the small board to attempt the solution.
• Daily Challenge: A new tsumego puzzle every day (determined by the calendar date). Includes a countdown timer to the next puzzle, a hint, and a local leaderboard to submit your solve time.
• Famous Games Viewer: Replay three legendary games move-by-move: the 1846 Inoue–Akaboshi game, AlphaGo vs. Lee Sedol Game 4 (2016), and the Atomic Bomb Game (Hiroshima, 1945). Each game includes expert commentary on key moves. Use ⏮ ◀ ▶ ⏭ to step through moves or Auto for automatic playback.
• Opening Library: Save any current game's opening moves with a custom name. Reload any saved opening to replay it on the board (same board size required). Saved locally — persists between sessions.

• Game Review Mode: After a game ends (or from the win screen), click ▶ Review. Step through every move of the game with ◀ ▶ buttons, jump to any move by number, and see the board state at each point. Exit with Exit Review.
• SGF Export: Click 💾 Save SGF to download your game as a standard .sgf file, readable by any Go software (Sabaki, GoReviewPartner, KataGo, etc.).
• SGF Import: In the Setup screen, use 📂 Load SGF to load any .sgf file for review in the built-in viewer.
• Move Tree: Click Move Tree to visualize all moves as a network of stone nodes. Click any node to jump directly to that position in review mode. Rebuilds dynamically.
• Board Snapshots: Click 📷 Snapshot at any point to save the current board state with a timestamp label. Up to 12 snapshots per game. Restore any snapshot instantly or delete individual saves. Access the gallery via the same button.
• Live Score Graph: Toggle Score Graph to see a real-time chart plotting estimated Black and White scores over the course of the game. Useful for identifying when the game shifted.
• Video Export: On the win screen, click 🎬 Export Video to render the entire game as an animated video file you can save. Shows each move with timing and effects.

Toggle Ambience to activate the cinematic time-of-day sky system, which reads your device's local clock and renders an accurate sky with the correct sun/moon position, stars, and atmospheric particles.

• Dawn (5–7am): Purple horizon fading to orange-pink. Sun rises from the east with warm atmospheric glow.
• Morning (7–10am): Bright blue sky, sun climbing, warm dust motes drifting.
• Noon (10am–2pm): Peak bright blue, sun near zenith, strongest board lighting.
• Afternoon (2–5pm): Slightly softer blue, sun descending west.
• Sunset (5–7pm): Deep orange-red horizon, sun disk with color shift, horizon glow.
• Dusk (7–9pm): Deep purple sky, fireflies appear near the horizon.
• Night (9pm–5am): Near-black deep navy sky, full star field with twinkling, realistic moon (with craters and phase shadow) rising from east to west across its arc. At 10pm you will see stars and the moon — not sunrise colors.
• Theme Particles: Cherry Blossom theme → falling petals; Cyber theme → electric sparks; Jade theme → floating leaves; Obsidian theme → rising embers.
• Board Lighting: The board receives a directional light effect matching the sun/moon position — warm gold at noon, orange at sunset, cool silver-blue moonlight at night.

• Stone Sounds: Black and white stones produce different pitched clicks on placement — generated with the Web Audio API to mimic the ceramic/slate sound of real stones.
• Capture Sounds: Capturing multiple stones produces pitched sounds that cascade with each stone removed — one sound per captured stone.
• Pass / Illegal Move Sounds: Distinct audio cues for passing and attempting illegal moves.
• Win Sound: A celebratory multi-note flourish plays on game end.
• Toggle: All sounds can be turned off with the Sound toggle button. Preference is remembered for the session.

• Stats Dashboard: Access via Stats button. Shows total games played, wins/losses, win rate, average game length, most common board size, and more.
• Win/Loss Streak Visualization: A row of colored pips showing your recent game results at a glance.
• Score History Chart: A line graph of your score across all recorded games.
• Full Game History Table: Every recorded game with date, mode, board size, result, move count, and duration.
• Export CSV: Download your complete game history as a .csv file for analysis in a spreadsheet.
• Clear Stats: Permanently delete all stored statistics (with confirmation).

• Place Stone: Click any empty intersection. A ghost preview follows your cursor.
• Pass: Click the Pass button (each player gets exactly one pass per game). When both players have passed, the game ends and scoring begins.
• Resign: Click Resign to concede — the opponent wins immediately.
• Undo: Click Undo to take back your last move (and the bot's response in PvE mode). Up to 10 undos stored per game.
• New Game / Setup: Access via New Setup button or after a game ends on the win screen. Returns to the full setup menu.
• Ko Rule: Enforced automatically — if a move would recreate a recent board position, it is marked illegal. A notification appears explaining the ko violation.
• Byo-Yomi Timer: Three pip indicators below the score show remaining byo-yomi periods. They dim as periods are consumed. The timer bar turns red when urgently low.

The four bots use progressively more sophisticated algorithms. All bots run entirely in your browser — no server required.

Pure random legal moves from all empty intersections. Zero strategy. Use to practice captures and basic patterns.

Weighted heuristics: prioritizes captures, rescues atari groups, avoids first-line moves early, targets star points. No forward search — pure pattern scoring.

Monte Carlo Tree Search (1.8s budget). Pre-filters top 28 candidates by heuristic score, then runs biased rollouts for each. Rollouts favor captures and atari, top-6 selection. Plays a strong, competitive game.

UCB1-based MCTS (3s budget, up to 6,000 simulations). Top 30 candidates. During rollouts, explicitly checks for captures first, then atari rescues, then strong scored moves. Final move selection by pure win rate. Significantly harder than Master — it reads captures, escapes, and territory systematically.

There are two main scoring systems used worldwide. They almost always produce the same result in well-played games, though they handle edge cases differently.

Score = Territory (empty intersections you control) + Prisoners (captured enemy stones).

• Dead stones left on the board at game end are removed and counted as prisoners.
• White adds komi (usually 6.5 points) to compensate for Black moving first.
• Filling in your own territory does not gain or lose points.
• This system requires agreement on which stones are dead before scoring.

Score = Territory + Living stones on the board.

• Prisoners are not counted — only the final board state matters.
• Filling your own territory reduces your score (territory decreases without adding stones).
• Komi is usually 7.5 points under Chinese rules.
• Less dispute about dead stones — if players disagree, they must play out the position.

Komi (コミ) is the point compensation given to White because Black moves first — a significant advantage. Standard komi values:

The half-point prevents draws. Because 6.5 cannot be exactly equaled by integer territory, there is always a winner.

Go has a beautiful handicap system that allows players of vastly different strengths to enjoy competitive games. Black places extra stones before the game begins, and White takes the first move. Each handicap stone roughly compensates for one rank of difference.

Go has a rich tradition of etiquette cultivated over millennia, particularly in East Asian cultures. Observing these customs shows respect for the game, your opponent, and the tradition.

• Nigiri: Before a game, one player grabs a handful of white stones; the other guesses odd or even by placing one or two black stones. If correct, the guesser plays Black.
• Rei: Both players bow (or say "yoroshiku onegaishimasu" — "please be kind to me") before the game begins.
• Pick up stones properly: Traditional players place stones with the index and middle fingers, snapping them onto the board with a satisfying clack.
• Do not pick up stones to deliberate: Once your hand lifts a stone over the board, you are committed to playing. Never hover indecisively.
• No take-backs: Once a stone is placed, it stays. Undo is only allowed by mutual agreement in casual games.
• "Otsukare sama desu": After the game, both players review and discuss the game — a tradition called nigiri or post-game review. Saying this phrase acknowledges your opponent's effort.
• Concede gracefully: If your position is clearly lost, resign rather than prolonging a hopeless game. This respects your opponent's time and demonstrates character.
• No analysis during play: Do not suggest moves to observers during a serious game. Kibitzing (commentary) is reserved for after the game.

• "Honte" (本手) — The "proper" or "correct" move. Sometimes the best move is the obvious, solid one. Don't overthink it.
• "Ikken tobi" (一間飛び) — A one-point jump. Considered the most efficient extension in many situations.
• "There are no bad moves, only bad positions." — Every stone teaches you something; learn from losses.
• "Lose your first 50 games as fast as possible." — The fastest way to improve is to play many games, even (especially) losing ones.
• "A rich man should not pick kos." — If you are winning, avoid risky ko fights. Protect your lead.
• "Play on the side of your thickness." — Attack toward your strong, thick groups to make the opponent's invaded stones weak.

Go uses a dual ranking system: kyu ranks for beginners (counting down to 1k) and dan ranks for advanced players (counting up from 1d). There is a gap between 1 kyu and 1 dan that represents a significant level jump.

• ~2500–4000 BCE: Go is believed to have originated in ancient China. Legend attributes it to Emperor Yao, who invented it to train his son's mind.
• ~500 CE: Go spreads to Korea (where it becomes baduk) and later Japan (go or igo).
• 17th century: Japan establishes the four great Go houses (Honinbo, Inoue, Yasui, Hayashi) under government patronage. Go flourishes as a state institution.
• 1603: Honinbo Sansa becomes the first Meijin (grand master), the highest title in Japanese Go.
• 1938: The "Atomic Bomb Game" — a famous game between Iwamoto Kaoru and Hashimoto Utaro that continued even after the atomic bomb dropped on Hiroshima nearby.
• 1968: Modern professional tournament system established in Japan.
• 1992: First Ing Cup (World Go Championship) — Go becomes international.
• 2016: AlphaGo (DeepMind) defeats Lee Sedol 4–1, the first AI to beat a top professional without handicap. Lee Sedol's one win (Game 4, Move 78) is considered one of the most remarkable single moves in history.
• 2017: AlphaGo Zero achieves superhuman Go ability by training entirely through self-play — no human games. Defeats AlphaGo 100–0.

This game features four AI difficulty levels, each using progressively more sophisticated algorithms. See the This Game tab for complete details.

Pure random legal moves. No strategy. Good for learning basic rules and captures.

Heuristic AI: captures when possible, rescues atari groups, plays star points. A real challenge for beginners.

Monte Carlo Tree Search with 1.8-second budget, biased rollouts favoring captures and atari, 28-candidate pre-filtering.

UCB1 MCTS, 3-second budget, up to 6,000 simulations, priority capture/rescue rollout logic, 30 candidates. Extremely difficult.