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Atlas: the four-colour map puzzle

Paint every region of the map with one of four colours — and never let two neighbours match. 2,000 verified maps (map coloring puzzles, if you spell it that way), from small and friendly to big and devious, with no ads and no sign-up.

Play Atlas How to play

How to play Atlas

The board is a map of irregular regions. A few of them start coloured (they carry a small dot). Colour the rest so that:

Every region gets one of four colours: yellow, blue, red or purple.
Two regions that share a border never have the same colour.

That's all. The four colour theorem promises any map can be coloured this way; the starting colours pin down exactly one answer, and you find it by logic alone — no guessing.

Controls

Pick a colour from the four swatches, then tap a region to paint it. Tap it again with the same colour to clear it.
Turn on Notes to jot down the colours a region could still be — small dots, like pencil marks. Colouring a region removes that colour from its neighbours' notes.
Two neighbours with the same colour get a red border between them, so clashes are easy to spot.
Prefer shapes to colours? Turn on colour symbols (● ▲ ■ ◆) in the game settings.

Atlas strategy: four techniques

Think in terms of what each region can still be. Every colour you place takes that colour away from all its neighbours. These are the techniques our hints use, from easiest to hardest, each on a real position from the game.

1. Last Colour

Look at a region's neighbours. If they already use three different colours, the fourth is the only one left — paint it. On easy maps this is all you need: each new colour sets up the next Last Colour.

Last Colour example: This region already touches yellow, blue and purple, so it can only be red. — **Real example from a Gooby game.** This region already touches yellow, blue and purple, so it can only be red.┅ the pattern✕ colour ruled out◯ region coloured● started coloured

2. Colour Pair

Two regions that touch each other and can both only be the same two colours — say blue and purple — will use one each. So any region touching both of them can be neither blue nor purple.

Colour Pair example: These two touching regions can only be blue and purple, one each. A region touching both can use neither colour. — **Real example from a Gooby game.** These two touching regions can only be blue and purple, one each. A region touching both can use neither colour.┅ the pattern✕ colour ruled out◯ region coloured● started coloured

3. Colour Triangle

The same idea with three: three regions that all touch each other and share only three colours between them use all three. A region touching all of them must take the fourth.

Colour Triangle example: These three regions all touch each other and can only use yellow, red and purple, one each. A region touching all three is left with none of them. — **Real example from a Gooby game.** These three regions all touch each other and can only use yellow, red and purple, one each. A region touching all three is left with none of them.┅ the pattern✕ colour ruled out◯ region coloured● started coloured

4. Dead End

Try a colour in your head. If it forces a neighbour to its Last Colour, and that one forces another, and soon some region has no colour left at all, the colour you tried was wrong — rule it out. Short dead ends are easy to see once you look for regions with only two options.

Dead End example: If this region were red, 2 highlighted regions would be forced, and then one would have no colour left. So it can't be red. — **Real example from a Gooby game.** If this region were red, 2 highlighted regions would be forced, and then one would have no colour left. So it can't be red.┅ the pattern✕ colour ruled out◯ region coloured● started coloured

Difficulty that adapts to you

There are no levels to unlock. Every finished puzzle updates your rating — clean, hint-free wins count most and a lost game lowers it — and the next map is chosen around your rating, with the odd easier breather and harder stretch.

Tier	Regions	What it takes
Easy	15 – 18	Last Colour only
Medium	18 – 22	A Colour Pair, or a long Last Colour chain
Hard	20 – 25	Several Colour Pairs and Triangles
Expert	23 – 28	One Dead End
Master	26 – 32	Two or three Dead Ends
Extreme	30 – 36	Four or more Dead Ends

Tiers are graded by the logic each map needs: the solver works through it the way a person would and counts which techniques it had to use.

Atlas questions

Why four colours?

The four colour theorem says any flat map can be coloured with four colours so that no two neighbouring regions match. Atlas turns that into a puzzle: some regions start coloured, and you work out the only colouring that fits.

Do regions that only touch at a corner count as neighbours?

There are no corner-only touches in Atlas. Every pair of regions either shares a clearly visible border, which means they must differ, or doesn't touch at all.

Do I need to guess?

No. Every puzzle has exactly one solution and is checked to be solvable by logic alone, using the techniques on this page.

Can I play Atlas offline?

Yes. After the first visit all puzzles are stored on your device, so it works with no connection. Add it to your home screen to use it like an app — here's how.

How does the difficulty work?

Atlas adapts to you. Each finished puzzle updates a skill rating, and the next puzzle is picked around it, from Easy maps of 15 regions up to Extreme maps of 36.