Petrus Method

Petrus Method

1. 2x2x2块

2. 扩展成2x2x3块

3. 修正朝向错误的棱块（Edge Control）

4. F2L-3rd & 4th（还原剩下的两对F2L，步骤c将使结果的顶层Cross已完成）

5. 顶层角块位置

6. 顶层角块方向

7. 最后4个棱块的位置

Petrus方法有很大的灵活性，可以有简单玩法，重复步数多，公式少，简单好记。也有高级玩法，第三步调整楞块朝向一步完成，第四步两对F2L一步到位，第五六七步适当合并。这使得它可以作为速度玩法和最小步玩法。

Step 1. Build a 2x2x2 block

Step 2 - Expand to 2x2x3

Step 3 - Twist the edges --- 2, 4 or 6 bad edges

Here are the four rules to remember:

1. An edge in the A layer that has an A color sticker next to the center is good.

2. An edge in the A layer that has an A color sticker away from the center is bad.

3. An edge in the B layer that has an A color sticker next to the center is bad.

4. An edge in the B layer that has an A color sticker away from the center is good.

Step 4 - Finish 2 layers

1.将R面的前下角块和与它相邻的两个棱块同时还原，或者将R面的后下角块和与它相邻的两个棱块同时还原。即先还原一个1X2X2的方块。

2.还原剩下的两个F2L。

Step 5 - Position the corners

Step 6 - Twist the corners

Step 7 - Position the edges

U Permutation : b U Permutation : a (R' U R') U' R' U' (R' U) R U R2 (R2 U') R' U' R U R U (R U' R)

Z Permutation H Permutation R' U' (R U') R U (R U') (R' U) R U (R2 U') R' r2 (R2 U) r2 (R2 U) U r2 (R2 U) R2 r2