Play

Something longer

These are longer than the games below. They keep your place on your own device, and nothing about them leaves this browser.

Let It Roll
Set out a few slopes, press GO, and watch the ball roll. When it misses, move one slope and run it again.
5 worlds to work through · keeps your place on this device · nothing here is timed
The Long Way Round
Draw one unbroken line that goes through every square exactly once.
5 worlds to work through · keeps your place on this device · nothing here is timed
Pack It In
Fit every shape into the frame with no gaps and nothing hanging over the edge. Five worlds, each asking a different question. Nothing is timed.
5 worlds to work through · keeps your place on this device · nothing here is timed
Slow Water
A patch of shallow water with a shoal in it. Feed them, and watch where the reef decides to grow. Nothing to solve, nothing timed.
keeps your place on this device · nothing here is timed
The Workshop
Every part is on the bench the wrong way round. Turn each one until the run is true, and build your machine a piece at a time.
5 worlds to work through · keeps your place on this device · nothing here is timed

Things to play. Each one teaches the idea in an article, and none of them keeps a score.

Phase Finder
The Moon's phase is where it is in its orbit, not a shape the Moon has.
About 5 minutes
Pole to Pole
A magnet has two opposite ends: unlike poles pull together and like poles push apart.
About 4 minutes

Close the Loop
A bulb lights only when current can leave the battery, go through it and come back: a complete loop, not just a connection.
About 4 minutes
Packet Path
The internet is a net: if one link breaks, the message finds another way.
About 5 minutes

Cloud Ladder
A cloud's name is built from two halves: how high it is gives the first half, and its shape gives the second.
About 4 minutes
Made of Air
Almost all of a tree's weight is carbon it pulled from the air, not stuff it took from the soil.
About 4 minutes
Make It Rain
Heat lifts water into the air, cooling turns it back into drops, and it falls again.
About 5 minutes
Pack the Comb
Hexagons leave no gaps and cost the least wall - they are what tightly packed circles become.
About 4 minutes

Fifteen
In a magic square every row, column and diagonal adds to the same number.
About 5 minutes
Narrow It Down
A guess is worth what it destroys, so cutting the middle of what is left beats a bold guess or a lucky one.
About 4 minutes
Shift the Wheel
Every letter of a Caesar cipher moves the same distance, so one number opens the whole message — and the message's own shape can hand you that number.
About 4 minutes
Ten Minus One
Nine times a number is ten times it with one taken from every row, which is what makes the tens digit one less and the digits add up to nine.
About 4 minutes

Mirror Wing
A symmetrical shape is one where every mark has a matching mark across the line.
About 4 minutes
Spin the Multiples
A bigger step does not draw a bigger figure. What decides it is sharing a factor with the ring.
About 3 minutes

Same Name
A name you can already read in one script unlocks the same symbols everywhere else.
About 6 minutes