By default, rotations are clockwise by 90°, but they can be anticlockwise when suffixed by a quote "'", or a U-turn when suffixed by the digit "2".
Simple face rotation: Right, Left, Up, Down, Front and Back
Directions are considered with respect to an observer in front of the face.
right face clockwise
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R | |
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left face clockwise
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L |  |
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up face clockwise
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U |  |
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down face clockwise
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D |  |
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fron face clockwise
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F |  |
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back face clockwise
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B |  |
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