The Waterwheel Sequence, with a minor modification, can be used to avoid the single half-twisted center at the end of the solve. After solving the corners (and before solving the edges), sum the twist of all six centers as shown. If the sum is a multiple of four (0, 4, 8, 12 or 16) then proceed normally (solve the edges then the centers) and there will not be a half-twisted center at the end. If the sum is not a multiple of four then use the Waterwheel Sequence with a half-twist on the fifth move (instead of a quarter-twist). Restore the corners with half-twists (as shown by the last four moves) and the solve can then be completed normally. Press the Random button to see more examples.
No Twist | 0 |
Quarter-Twist Clockwise | 1 |
Half-Twist | 2 |
Quarter Counter-Clockwise | 3 |
"Solvable" in the above tables refers to whether it can be solved
without getting the single half-twisted center at the end.
After the sequence the center on the top face is half-twisted and the sum
shows that the configuration is solvable, it will remain that way during the
solve of the edges.
These examples always show a configuration where the sequence is needed
but when solving scrambled cubes half of them would already be solvable.
The last four moves of the sequence, which restore the corners with
half-twists, can be done many different ways (16 to be exact).
While these have varying effects on the centers the result is always a solvable
sum which is all that is needed prior to solving the edges.
In other words, it works no matter how it is done.