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, and every spot on it belongs to whichever iguana stands closest, so each border runs halfway between two neighbours. On your turn you do one thing: tap a region to hatch a second iguana beside one standing alone, or drag an iguana anywhere its region reached before you started. Hold more than half the island when your turn starts and you take a point, and the other colony loses every point it had. Three points wins.

The rules

Land iguanas are territorial. Every spot on the island belongs to the iguana standing closest to it.

A dark iguana walks toward a yellow one and the border between their two colours slides along with it, staying halfway between them.
Move an iguana and the borders follow, always halfway between neighbours.
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.
Tap a region and a hatchling appears beside its iguana — no ground changes hands yet. Only an iguana standing alone may hatch: never three on a spot.
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.
Or drag an iguana, which may finish anywhere its region reached before you started.
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.
Hold more than half the island when your turn starts and you take a point — and the other colony loses every point it had. Three points wins the island.

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 hatchling takes no ground on the turn it is laid; it pays later, when the two walk apart and hold more 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 hold now but how much you will still hold once the other colony has moved.

In a classroom

Gordon Hamilton, 2026. Eleven plain shapes against one rival, which hatches where the shared border is longest, walks to the spot that holds the most island, and never hatches when a hatchling 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