Voronoi Islands

Every spot on the island belongs to the nearest iguana, so the game is where to stand to hold more than half of it.

The Voronoi Islands board

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Grades
2–6
Subjects
Shapes & Space, Fractions, Logic
Kind
Two-player game
Cost
Free, no account, no ads

What it is

Two colonies of Galápagos iguanas share an island. Iguanas are territorial: every spot on the island belongs to the iguana closest to it, so each border runs halfway between two neighbours. Each turn you do one of two things: move an iguana within its existing territory, or tap an iguana and it reproduces. If you own more than half the territory at the start of your turn, your opponent loses all their points and you get a point. Three points wins the game.

The rules

A dark iguana walks toward a yellow one and the border between their two colours slides along with it, staying halfway between them.
Iguanas are territorial. Every spot on the island belongs to the iguana closest to it.

Each turn you may either:

A dark iguana walks across its own region toward the yellow one and the border swings after it; the region it set out from is drawn as a dashed outline, and an arrow leaving that outline is crossed out.
1) move an iguana within its existing territory.
A dark region with one iguana on it becomes the same region with two iguanas standing on the same spot; not one border moves, and the region is not divided until one of the two walks away.
2) Tap an iguana. It reproduces.
The same island three times over, dark holding more than half of it each time, with one more pip filled underneath at every turn until all three are dark.
At the start of your turn, if you own more than half the territory, your opponent loses all points and you get a point. You win the game if you have three points.

What it gives you to practise

Area you can watch move. A border is the line halfway between two iguanas, so a step toward a neighbour pushes the border toward them by half as much, and the share over the board answers at once. A new iguana takes no territory on the turn it appears; it pays later, when the two move apart and cover more ground than one could alone. And because a point is scored only at the start of your own turn, the question is never how much you own now but how much you will still own once your opponent has moved.

In a classroom

Gordon Hamilton, 2026. Eleven plain shapes against one rival. It makes an iguana reproduce where the shared border is longest, moves an iguana to wherever it would own the most territory, and never reproduces when the new iguana would hand you the match. Six of the shapes are measured even for two people, for a hot seat on one tablet or an online room. The board prints as an empty island with the two landings marked, for pencils.

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The whole game at one address, with every board in it. Whoever opens it stays inside it, and their progress stays in their own browser.

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Near it on the shelf