Test notation, inverse sequences, cross correctness and choice of solving method with six original exercises and expandable answers.
In this guide
1 · Undo a short scramble
A solved 3×3 is scrambled using R U F2. Which sequence certainly restores it?
Answer and explanation
F2 U′ R′. Reverse the order, then invert each move. F2 is its own inverse. Keep the whole cube orientation fixed.
2 · Is the cross finished?
All four lower edges show white down, but the front edge shows red above a green centre. Is that sufficient?
Position as text
Geometrically calculated 3D teaching view. White cross with the white face held upward; side colours are greyed out to explain the pattern.
Answer and explanation
No. Each side colour must match its centre too. Check every white edge and place it between the correct centres.
3 · 90° or 180°?
You try a 90° turn of a non-square side on a rigid 3×3×2. What must shape-preserving play account for?
Answer and explanation
That turn does not fit the rectangular cross-section. Our edition replaces incompatible quarter turns with half turns or disables them; a 3×3 algorithm is not automatically executable.
4 · One colour, still unsolved
A silver Mirror Cube has one colour everywhere but unequal heights. What is its goal?
Answer and explanation
Restore the original cube shape with flush faces. Widths and heights identify pieces instead of colours.
5 · A sequence and its inverse
For A = R U R′ U′, what is A⁻¹? Is changing primes in the original order enough?
Answer and explanation
A⁻¹ = U R U′ R′. The order must also reverse. A followed by A⁻¹ restores any starting state.
6 · Two pyramids, different methods
Pyraminx and Mastermorphix both resemble pyramids. Should you use identical algorithms?
Answer and explanation
No. Pyraminx uses vertex axes; Mastermorphix modifies a 3×3. Identify the mechanism and piece types first.