Sim is one of those wonderfully compact yet deeply satisfying strategy games that rewards clear thinking and forward planning. If you have ever wondered how to play Sim game for the first time, you are in for a pleasant surprise — the rules are simple enough to learn in a matter of minutes, yet the gameplay offers enough depth to keep players engaged across dozens of sessions. All you need is a pencil, a piece of paper, and a willing opponent. No screens, no batteries, no complicated setup. Just pure geometric thinking between two players.
The game was invented by Gustavus Simmons in 1969 and has since become a beloved puzzle and game theory classic. It sits comfortably in the tradition of pencil-and-paper games, alongside noughts and crosses and dots and boxes, but offers something those games cannot quite match — a mathematical guarantee built into its very structure. Understanding how to play Sim game properly means grasping this guarantee from the outset: in Sim, a draw is mathematically impossible. Someone must win every single time.
Setting Up the Game
Before you explore how to play Sim game in practice, you need to draw the board. Begin by marking six dots arranged in a perfect hexagon on a blank piece of paper. Label them or simply place them evenly around a circle — the exact size does not matter, as long as all six points are clearly visible and roughly equidistant from each other. This hexagonal arrangement of six vertices is the entire playing surface for Sim.
Each of the six dots represents a vertex, and the game will be played by drawing lines between these vertices. With six vertices in total, there are fifteen possible line connections between them — every dot can be joined to every other dot. These fifteen edges form what mathematicians call a complete graph, specifically K₆, and it is the properties of this complete graph that make the game both fair and fascinating. You do not need to pre-draw any lines; they will be added one at a time as play progresses.
The Core Rules
Learning how to play Sim game is straightforward once the board is in place. Two players take turns, and each player is assigned a colour — traditionally red and blue, though any two contrasting colours of pen or pencil will do. On each turn, a player draws a single line connecting any two dots that have not yet been connected. That is the entire action required each turn: one line, between two previously unconnected vertices.
The player who is forced to complete a triangle of their own colour loses the game. This is the central rule of how to play Sim game, and everything else flows from it. A triangle in this context means three dots all connected to each other by lines of the same colour — a closed loop of three edges belonging to one player. The moment such a triangle appears on the board, the player whose colour forms it is declared the loser.
Notice that the losing condition is framed as completing a triangle, not as creating one deliberately. This matters because the game often forces players into difficult positions where every available move risks closing a triangle. The strategic challenge, then, is to delay this outcome for as long as possible while engineering situations where your opponent has no safe moves left.
Why a Draw Is Impossible
One of the most remarkable aspects of how to play Sim game — and what sets it apart from most pencil-and-paper games — is its mathematical certainty. A draw cannot occur. This is not a rule imposed by convention but a theorem proved by Ramsey theory, a branch of combinatorics. Specifically, it can be shown that in any two-colouring of the edges of K₆, at least one monochromatic triangle must exist. In plain English: once all fifteen lines have been drawn between the six dots using only two colours, at least one triangle of a single colour is guaranteed to appear. The game cannot end without a winner.
This knowledge shapes how to play Sim game tactically. Because the board must eventually produce a same-colour triangle, both players are fighting a rearguard action — not racing to score points, but manoeuvring to ensure the inevitable triangle belongs to the other person. This gives Sim an unusual tension. Unlike games where you strive to achieve something, Sim asks you to avoid something, and that shift in mindset makes the game feel fresh each time.
Basic Strategy
Now that the rules are clear, it is worth considering the strategy behind how to play Sim game effectively. Beginners often focus purely on avoiding their own triangles without paying attention to the positions they create for their opponent. Strong players do both simultaneously — they think several moves ahead, anticipating which edges will become dangerous traps.
A useful starting principle in how to play Sim game is to watch the degree of each vertex carefully. The degree of a vertex is simply how many lines of a particular colour connect to it. If one of your coloured edges touches a vertex already connected to two other edges of your colour, you risk closing a triangle with your very next move at that vertex. Keeping this count in mind for every vertex on the board helps you identify which areas are becoming dangerous.
Another sound strategy when considering how to play Sim game is to spread your lines across different parts of the board early on, rather than clustering several connections around the same few dots. Concentration leads to triangles. By distributing your edges more evenly, you keep your options open and reduce the risk of boxing yourself in during the later stages of the game, when fewer safe moves remain available.
The Middle and End Game
As the board fills up, the character of how to play Sim game changes noticeably. Early play tends to be exploratory, with both players establishing lines across the hexagon. By the middle stages, roughly eight to twelve lines in, the pressure begins to mount. Certain vertices will have acquired several coloured edges, and the number of truly safe moves starts to shrink.
This is where genuine strategic depth in how to play Sim game reveals itself. A skilled player will try to construct what might be called a forcing sequence — a series of moves that progressively narrows the opponent’s options until they have no safe line left to draw. The opponent then must complete a triangle of their own colour, regardless of which edge they choose, and the game ends.
In the final stages, it is common for both players to be operating with very limited safe moves. Counting carefully, tracking all existing edges by colour, and visualising potential triangles before committing to a move are all essential skills. Players who internalise the board geometry quickly will find their results improve considerably.
Tips for New Players
For anyone just beginning to explore how to play Sim game, a few practical tips can speed up the learning curve. First, redraw the hexagon large enough to write clearly inside — cramped boards lead to misreads and disputed triangles. Second, use colours that contrast strongly; faint pencil against dark ink can cause confusion mid-game. Third, after each completed game, take a moment to trace back through the moves and identify the point where one player’s position became inescapable. This retrospective analysis is the fastest way to improve.
It also helps, when learning how to play Sim game, to accept early losses as a natural part of the process. The game’s strategic layer only becomes visible after you have experienced the discomfort of being gradually cornered. Once you feel that pressure from the inside, you begin to understand how to impose it on others.
Why Sim Endures
Sim endures because it achieves something rare in abstract games: it is both provably fair and genuinely surprising. Every game ends in a decisive result, yet the path to that result is never quite the same twice. The fifteen edges of the hexagonal board offer enough variation to sustain repeated play without repetition becoming a problem.
Understanding how to play Sim game also opens a small window into the wider world of combinatorics and graph theory, making it a quietly educational experience alongside its entertainment value. Teachers have used it to introduce students to mathematical thinking; puzzle enthusiasts have used it to sharpen their spatial reasoning; and casual players have simply enjoyed it as a beautifully self-contained game that fits on a napkin.
Whether you are playing for the first time or returning after years away, the principles of how to play Sim game remain constant: draw the hexagon, take turns adding coloured edges, avoid completing a triangle in your own colour, and think at least two moves ahead. Master those fundamentals, and you will find Sim to be one of the most rewarding pencil-and-paper games ever devised.