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Fold the cube

Six labelled squares fold into a cube. Which face ends up opposite this one? Which two never touch? Is it a proper die? All eleven nets.

  • Spatial
  • Untimed
  • 5 levels

How it plays

The board is a net: six squares that fold up into a cube. Fold it in your head and answer — which face is opposite the one named, which of the listed pairs are opposite, or whether a numbered net makes a proper die, where opposite faces add up to 7.

A way in: put the named face down. The squares beside it fold up as its four walls; whatever is left is the lid, opposite it. Two squares in a line with one square between them always end up opposite.

Levels bring the harder nets — from the band-of-four crosses to the staircase — and then the harder questions. There are eleven nets and three questions, so the levels stop there; each net is laid any of eight ways and labelled afresh every time.

Keys

Space starts and skips ahead · 1–9 pick · Enter submits · Esc stops. On a phone, tap.

What it trains

This practises folding cube nets in the head, as the cube and dice questions of aptitude tests ask. It claims nothing about spatial ability in general.

Learn

How to get better at fold the cube: the method, the techniques, what each new level asks of you, and the traps the wrong answers are made of.

Your approach to each question

  1. Read which question it is: the face opposite one named face, which listed pair is opposite, or whether a numbered net makes a proper die.
  2. Find the three opposite pairs with the rules below before you look at the options. Every net has exactly three pairs, and every face is in one of them.
  3. Cross out what cannot be opposite: any two squares that share an edge in the net, and any two that touch at a corner, end up sharing an edge on the cube.
  4. If no rule fits, fold for real in your head: put the named face down, lift its neighbours up as walls, and see which square is left over for the lid.

Techniques and tricks

  • One square between, in a line

    Two squares in the same row or column with exactly one square between them always fold opposite.

    e.g. In the band of four A B C D, A is opposite C and B is opposite D

  • The ends of a Z

    Four squares in a Z or S shape — two side by side, and two more side by side in the next row, overlapping by one — fold with the two end squares opposite. This settles the staircase and the 2-3-1 nets.

    e.g. Net rows “AB..”, “.CDE”, “.F..”: A, B, C, D make a Z, so A is opposite D

  • Flaps on both sides of a strip

    A square stuck to the top of a straight strip and one stuck to its bottom are always opposite, wherever along the strip they sit.

    e.g. The cross with a flap above the first square and a flap below the third: the two flaps are opposite

  • Neighbours never face each other

    Squares that share an edge in the net share an edge on the cube, and so do two that touch only at a corner. Rule them out first.

    e.g. A square’s four net neighbours can never be its opposite, whatever the options say

  • Three pairs, six faces

    Once you have found two opposite pairs, the third is the two faces left over. You rarely need to work out all three.

  • Dice: test each pair against 7

    For “is it a proper die”, find the three opposite pairs and add each. All three must make 7. In this game a wrong die has two faces that share an edge swapped, which always breaks two of the sums.

    e.g. Pairs 1–6, 2–4, 3–5: 2 + 4 = 6, so No

As the levels climb

  • You start on the six 1-4-1 nets: a band of four with one square above and one below. The line rule and the flap rule answer everything here.
  • Next come the 2-3-1 nets: a band of three, with two squares stepping off one end on top and one square below. The Z rule is the one you will need most; look for the two squares stepping off the row.
  • Then the pair question joins: which listed pair is opposite. Find the pairs first, then scan the options for one.
  • The staircase and the 3-3 net arrive, then the die question, and the ladder stops: eleven nets, three questions. Every net is still laid any of eight ways, turned and flipped, so learn the rules by shape, not by position on the screen.

Traps to avoid

  • The far-apart square: the wrong options are the squares farthest from the named one in the net. Distance on the page means nothing — the two ends of a band of four are far apart and still share an edge.
  • For the pair question, the lures are pairs that lie far apart in the net but meet once folded. Confirm a pair with a rule, not with the gap between them.
  • Saying a face is opposite one it touches at a corner. Two squares that meet only at a corner fold edge to edge.
  • On the die question, checking one pair and stopping. A swap breaks two pairs and leaves one at 7, so the pair you happen to check may look fine.

How to practise

  • Untick everything under Questions except “Which face is opposite” until the line, Z and flap rules come at a glance, then add the other two.
  • Switch Faces marked with to Symbols once letters feel easy: you cannot lean on alphabetical order to keep track of the pairs.
  • On a wrong answer, read which face the working puts face down and which four become walls, and replay the fold in your head with that face down.
  • Cut a cross of six squares from paper once and fold it. Seeing the line and flap rules happen in your hands is what makes them believable on screen.

Levels

It is untimed unless you turn the clock on. There are 5 levels with the default settings, and the counter stops at the real top. Your level is judged on your last ten answers, every ten: 90% moves you up, below 80% moves you down, which holds most people near four in five right.

All of it is in the settings beside Start — how many answers a judgement looks at and how often it recalibrates, the thresholds, the time, which questions, how many options, and whether you see each verdict at once or review them together at the judgement. You can also jump to any level.

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