Learn · the Skewb
The cube that cuts corners
The same shape as a Rubik's Cube and almost nothing else in common: the cuts run corner to corner, so every turn swings half the puzzle at once. Strange to look at, quick to learn.
Pick up a Skewb and the first surprise is that there is no face to turn. Grab a corner and twist instead: half the puzzle comes with it. Only four axes do anything, named U, L, R and B after the corners they run through, and a bare letter means turn that corner clockwise as you look straight at it.
The second surprise is how small the puzzle is. Four of its eight corners can never leave their places and only twist where they stand; the other four corners and the six face centres are everything else. A Skewb has 3,149,280 positions, and a computer sweep of all of them says the very worst is 11 turns from solved. A Rubik's Cube has forty-three quintillion.
One. Build one face, by eye. Choose a colour and make that whole side solid: its centre and all four of its corners. There is no algorithm and nothing to memorise. Turn corners freely, watch pieces arrive, and undo anything that goes wrong. This is the part that feels impossible for ten minutes and then never troubles you again. Hold that face downwards from here on and do not turn the puzzle over.
Two. Place the top corners. Look at the four corners on top and ask only whether each is in the right place, ignoring which way round it sits. Getting them home is short intuitive work: turn a top corner, see what arrives, put it back. Most solves need only a couple of tries, because there are just four corners and one of them is usually already right.
Three. Turn the corners the right way round. Now the twisting. U R L' B' L' R' U B turns four corners where they stand and does nothing else whatsoever: no piece travels, no centre moves, and your bottom face survives. Re-angle the puzzle between goes until every corner reads correctly.
There is less to recognise here than you would expect. With the bottom face solid and every corner in its place, only nine of the eighty-one ways four corners could be turned can actually occur, and allowing for how you hold the puzzle those nine are two cases: two corners turned, or all four. Two corners turned are always diagonal to each other. Side by side cannot happen, and that one restriction rules out most of the rest.
Four. Send the centres home. What is usually left is two or three centres in each other's places. U L' B' L B R' U' R cycles exactly three centres and touches nothing else at all. Play it, look, re-angle, play it again, and the puzzle finishes.
Left: the corner twist, four corners turning where they stand. Right: the centre cycle. Both run on the same geometry the sweeps proved.
Those two sequences came out of a search for the shortest sequences, up to eight moves, that leave a finished bottom face solid and disturb one kind of piece only. Each does exactly one job: the first twists 4 corners and moves nothing else at all, the second cycles 3 centres and moves nothing else at all. How many goes a particular scramble needs is another matter, and that part is ordinary practice.
Getting faster works the way it does on every other puzzle: plan the first face during inspection, then finish in fewer looks. The coaching pages apply unchanged, and the timer will count for you.
The engine behind this page is checked two ways before publishing: a geometric model that rotates stickers in space, and a compiled model that reduces each move to a permutation, which must agree. The position count and the eleven-turn figure are re-derived by sweeping the whole puzzle, and each algorithm's effect is re-measured. The method itself is the standard beginner one and is not claimed to be the shortest route.