How to play Dodgem

Dodgem is a small, sharp racing game for two players. You and your opponent each drive a few cars across a square grid, but in different directions: your cars head up the board, the opponent's head across it to the right. Every car has to cross the other side's path, so the game is a constant tug between getting your own cars out and getting in the way of theirs.

The game was devised by Colin Vout and became well known through the mathematical games book Winning Ways for your Mathematical Plays. The board is tiny, but it is a pure game of skill: there is no chance, and a single wasted move can decide the race.

How to play on skill.games

• Start a game. The settings window opens first: choose a difficulty and a board size, then press PLAY.
• Make a move. Tap one of your green cars. Green dots show the squares it can drive to. Tap one to move, or tap a different car to change your mind.
• Drive off the board. Faint chevrons mark the exits beyond the far edge: green ones above the top row for your cars, orange ones to the right of the board for the computer's. When one of your cars sits on the top row, tap it and then tap the dot on the exit above it, and it drives away.
• Who moves first. You always make the first move.
• The score line at the top shows how many cars each side still has on the board.
• Pause. The menu button in the top-left corner pauses the game, with options to resume, start a new game or switch the sound off.
• Saving. Your game is saved after every move. If you leave mid-game, choose CONTINUE next time to pick up where you stopped.
• Results. The end screen shows how many cars each side got off the board, what decided the game and how many moves were played, plus your wins, losses, draws, win rate and streaks for that board and difficulty.

Rules

Setup. On a board of N × N squares, each side has N − 1 cars: 2 cars on 3 × 3, 3 on 4 × 4 and 4 on 5 × 5.

• Your cars fill the bottom row, except the bottom-left corner. They drive up.
• The computer's cars fill the left column, except that same bottom-left corner. They drive to the right.

Moving. On your turn you move one car by exactly one square, onto an empty square. A car may move:

• forward (up for you, right for the computer), or
• sideways (left or right for you, up or down for the computer).

A car can never move backward, and cars never jump over or capture each other: a car with other cars on every square it could move to is stuck until one of them moves.

Leaving the board. A car on the far edge (the top row for you, the right-hand column for the computer) may use its forward move to drive off the board. That car is out of the game for good, and that counts as progress.

Winning.

1. The first player to get all of their cars off the board wins immediately.
2. If it is a player's turn and none of their cars can move because they are all blocked, that player wins. In other words, you must always leave your opponent a legal move. Block too completely and you hand them the game.

Draws. If neither side has won after 120 moves in total (60 each), the game is a draw.

Strategy tips

• Count the race. Add up how many moves each side needs to get every car off: the distance to the far edge, plus one to exit, for each car. If you are behind, you must slow the computer down rather than just drive.
• Block with forward progress. The best blocking moves also move your car closer to the exit. A car parked directly in front of an enemy car forces it to waste a sideways move to get around.
• Sideways moves cost time. Every sideways step is a move that brings no car closer to the edge. Use them only to dodge a block or to set one up.
• Do not trap everything. Since a player with no move wins, completely sealing the computer in is a mistake. Leave it a move, ideally one that costs it time.
• Keep escape routes. A car with only one free square next to it can be shut in by a single enemy move. Prefer squares where your car still has a choice.
• Exit at the right moment. Driving a car off is usually good, but a car on the top row may be blocking an enemy car. Sometimes it pays to keep it there one more turn.

Difficulty levels

• Easy looks only at its own move, and about a third of its moves are random.
• Normal looks a few moves ahead and only occasionally plays a random move.
• Hard looks several moves ahead and almost never plays a random move.
• Crazy looks the furthest ahead and never plays a random move. Every level always takes a winning move when it sees one.

Modes

Three board sizes are offered:

• 3 × 3, Classic with 2 cars each, the original game and the default. Very few moves are possible, so every single one matters.
• 4 × 4, Medium with 3 cars each, with more room to dodge and more ways to block.
• 5 × 5, Big with 4 cars each. The traffic is heavier and the races are longer, so planning blocks several moves in advance becomes the key skill.

Statistics are kept separately for each board and difficulty.