To make the bottom cross in one step, which is the CROSS in CFOP, there is an article called the Cross Heavenly Book (authored by Zhang Xuqi), which specifically explains the cross.
The following is the full text:
When we first learned the Rubik's Cube, the way to make a cross was to sequentially cut the four bottom edges (referring to the four background-colored edges that make up the cross) , hereafter referred to as the edge block) is adjusted to the correct position. This is a method that is easy to understand and master. If you want to use this method to quickly complete the cross, you need to quickly respond to the various states of a single edge block and restore it with simple and convenient steps. Here are a few examples:
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2009-7-28 12:23
Because the finished edge blocks cannot be destroyed, it takes 2 to 3 steps to adjust each edge block, one*** On average, it takes 8 to 12 steps, which is too long. Moreover, it is difficult to take into account other edges when making one edge. A common method is to make one edge and then look at the next one. This way, you have to pause three times. Not only is the cross speed very slow, but the first 15 seconds of observation are also difficult. to effective use.
If an edge happens to be in the right position, we will preconceptions and use it as the starting point, and the result will be misled. To give the simplest example:
Restore the Rubik's Cube, With the top color facing up, do R' D R.
At this time, only the edges on the R surface are correct, so if we restore each edge in turn, the best step is probably as follows:
R U R' F2 Make F The edge block of the surface
U L2 Make the edge block of the L side
U B2 Make the edge block of the B side
Steps one to eight, It can be done quickly through optimization techniques, but by reversing and scrambling the formula, we know that we can make a good cross by just doing R'D'R. The problem is that all our thinking starts from the correctness of the R-surface edge block. , but in fact we were misled by the fact that the R-surface edge block is correct.
The method of making a cross that I want to teach you today is to make full use of the 15 seconds of observation time to establish the correct relative position of the edges, and then make the final adjustment. During the adjustment process, observe the first set of F2L. The total number of steps does not exceed 8 steps.
Forget
First of all, don’t be misled by the edges that are already in the correct position, because the edges that seem to be correct now may be incorrect in the relative position relationship, which will make us think misleading. So the first step we have to do is to turn a blind eye to the color of the current center block and forget about them. If you can't do that, you can remove the center block covers on the four sides when practicing the cross...
Remember
Because there is no hint of the color of the center block, we must memorize the order of the center colors on the four sides...
View
Get the shot After messing up the Rubik's Cube, first look through the entire Rubik's Cube quickly, and quickly remember the distribution and correct situation of the four edges...
Check
First find a group with an average number of edges per It is an edge block that can complete the relative position relationship on the bottom layer using at most two steps of rotation (the structural relationship of this group of edge blocks is called the base point, and this group of edge blocks is called the base point edge block. The edges that are not included in the base point are called The block is called a non-base point edge block), and then proceed to the next step of reasoning...
Color
After finding the base point, the next step is to redefine the color of the side center block, that is, use Use imagination to color the Rubik's Cube in our hands, and determine the colors of the four side center blocks based on the colors of the two base point edge blocks and the order of colors we have memorized. Because you can see the color of the base point edge block, you actually only need to color the side center block that is not the base point...
Push
Because the correct block is the most used Step 2 can definitely be restored, and the restoration process is quite simple. It can be completed by temporary judgment and conditioned reflection. Therefore, after completing the base point, as long as we confirm that the remaining edge blocks are correct blocks, we can end the reasoning and start making base points.
Of course, if you have restored 3 underlying edge blocks within 4 steps, then it does not matter even if the last one is an incorrect block. You can just use the method mentioned above to restore it. With the final adjustments, the total number of steps will not exceed 8. step. However...
Upgrade
Basic point upgrade means adding an edge block to the basic point system through 1 to 2 steps of rotation without destroying the original basic point. , there are generally two methods...
Repair
In most cases we can find an upgrade solution, and some do not even need to upgrade (directly three base points), Then we only have the last block left. If it is the correct block, then the reasoning is over. If it is the wrong block, it is best to correct it to the correct block during the restoration or upgrade of the base point...
OK
After the reasoning is over, it’s time to put it into practice. Except for special circumstances (three blocks are completed in 4 steps and one wrong block is left, or all blocks are on the bottom layer... etc.), all we have to do is complete the basic points (With the upgrade process), fix the wrong blocks by the way, and finally put the correct blocks in order...
End
If everything goes well in the previous step, build a cross after completing the base point The rotation of u and or D is not used in the process, so just use u or D to directly adjust the final adjustment angle we remember. If there is a rotation of U or D during the process of making a cross, then the adjustment angle originally memorized cannot be used. At this time, the final adjustment can be completed by re-judging the color of the edge block and the center block on the F surface...