Recognize a dot, an L, a line, or a cross using only the four top edges.
By the end: orient the yellow edges while preserving the completed bottom two layers.
Keep yellow up. Ignore all four corner stickers. Count yellow only in the four edge positions around the yellow center. A legal cube with two solved lower layers has zero, two, or four such yellow edge stickers.
Zero is the dot case. Two adjacent yellow edges make an L; two opposite ones make a line. Four make the cross. One or three means you should first recheck the lower layers and your reading of edges versus corners. Do not immediately assume the physical cube needs repair.
An edge has two stickers attached to one piece. On the upper face its sticker occupies the middle square of an outside row, never a corner square. The four squares that matter touch the yellow center along a side. Read them in order, back, right, front, left. Say whether each is yellow. This gives a description you can compare after a turn without being distracted by a corner that happens to have yellow facing upward. The center itself is your reference, not a fifth edge.
At entry to this stage, every piece outside the upper layer should already match its centers. Check the white face underneath and the two lower rows around all four sides. The solid drawing shows only some faces; use the unfolded net for the rest. On a physical cube, inspect missing sides with a regrip and return to your front before starting a sequence. A completed middle layer means the remaining four edges all contain yellow, even when their yellow stickers face sideways rather than upward.
Orientation means which direction a piece's stickers currently face. Location means which slot holds that piece. Here, an edge is oriented when its yellow sticker faces up. Its other color might still be above the wrong side center. That is allowed at this checkpoint. Picture the yellow-green edge with green on top and yellow facing front. This yellow edge contributes no yellow square to the top cross. We must move the whole piece through legal turns, not pretend that the upper green sticker is yellow.
The dot, L, line, and cross names describe only those four upper edge squares. A dot can have several yellow corners around it. An L can sit inside what looks like a mostly yellow face. Cover the corner squares with your fingers if their colors distract you, leaving the center and edges exposed. Then distinguish adjacent yellow edges, which meet around a corner of the face, from opposite yellow edges, which lie across the center. That difference determines the next setup, even though both cases contain two yellow edges.
Why can you see zero, two, or four upward yellow edge stickers, but not an isolated one in this prepared stage? Legal turns cannot leave just one edge flipped while every other edge has its solved orientation. Edge flips must balance in pairs. Once the lower two layers are solved, any remaining flips belong to the four yellow edges. An even number must face sideways, so an even number also faces up. This constrains a legally turned, prepared cube; it does not remotely certify your physical puzzle.
If you count one or three, stop before choosing a case. First recount the middle squares, excluding the center and corners. Next inspect the lower layers, including hidden faces. An unfinished middle edge invalidates the entry condition, so the dot and line decision rule is not yet applicable. If the simulator was at a prepared state, Undo can reverse a known accidental turn. An unusual physical pattern needs separate investigation. This lesson does not ask you to remove pieces, peel stickers, or force an individual edge to flip.
Use F R U R' U' F'. This is a front turn, the familiar right four-move group, then the inverse front turn. For a line, hold its yellow edge stickers at left and right. For an L, hold them at back and left. For a dot, any front face works.
Complete the six moves and inspect the new pattern. A correctly held line becomes a cross. A correctly held L becomes a line, which must be inspected and set up again. A dot requires more applications. Regrip or turn U to establish the stated shape between applications; never guess by corner colors.
An algorithm is a fixed sequence of legal turns used from a specified setup. This one has six written moves. The first F opens the front layer, then R U R' U' moves pieces through the upper and right layers, and F' closes the front layer again. The middle four moves are familiar, but their job depends on this setup. That familiar group helps recall the letters; its white-corner target and stopping test do not apply here. Keep the same front throughout all six moves.
Follow the Horizontal line example through its actual intermediate states. Initially the left and right upper edge squares are yellow, while the back square is green and the front square is red. These squares do not mean that middle-layer edges are missing. The yellow-green edge is at upper-back with green up, and the yellow-red edge is at upper-front with red up. Their yellow stickers face sideways. The sequence will reorient the yellow edges and rearrange their locations while returning the lower layers at its boundary.
After the first F in this example, the front upper edge square becomes orange. The upper edge colors, read back, right, front, left, are now green, yellow, orange, yellow. This is not a shape-rule decision point because the front layer is open and the lower layers are disturbed. Continue R, U, R', U'. After these five total moves, the upper edge colors in that same order are yellow, yellow, orange, yellow. The tempting three-yellow count is an intermediate state, not evidence that the prepared cube was illegal.
The final F' brings the remaining yellow sticker upward and restores the lower layers. All four upper edge squares are now yellow. In this particular prepared example the side edge stickers also match, because the example was constructed by reversing the six moves from a solved cube. That extra success belongs to this start, not the yellow-cross promise. On another legal start the yellow cross may sit above wrong side colors. Check the actual cross goal rather than requiring the whole demonstration's final appearance on every scramble you solve.
The line setup is geometric. Viewed straight down at U with the chosen front toward you, yellow must occupy the left and right edge squares. If the yellows instead occupy front and back, a quarter turn of U makes the line left-right without touching the lower layers. A vertical regrip also changes your front and right. Choose one setup action and inspect afterward. Do not add a setup turn halfway through the algorithm. Once F begins, the six moves refer to the grip you just established.
Compare two starts that differ by one U turn. One has a left-right line and the other a front-back line. Running the same six moves from both starts does not have the same useful result. The unprepared line does not become a cross. This shows why recalling only the letters is insufficient. If you discover the setup error in practice, undo the known turns to the original state or restart the case. Then set the line correctly before trying again. Extra front turns do not repair forgotten setups.
At this stage, side colors on the yellow edges need not match their centers. We are orienting the edges, not finishing their positions. The next lesson handles the side-color matches.
If you already have the yellow cross, skip the algorithm. Repeating it on a cross can remove the very checkpoint you have reached. Always recognize the current case before choosing a sequence.
For the L, use back and left as the two yellow directions. These are adjacent edges around the upper-back-left corner, but the corner sticker itself can be any color. In the top diagram, back is the upper edge of the square and front is the lower edge. That convention matters when reading a net rather than holding a cube. An L drawn like the familiar letter may face the wrong way. Name the two occupied edge positions instead of rotating the picture mentally until its outline seems familiar.
In the Back-left L example, the initial upper edge colors read yellow at back, green at right, blue at front, and yellow at left. Finish the six moves once. The upper edge colors are green back, yellow right, red front, and yellow left. You now have a left-right line, so the same grip already suits the next application in this prepared example. Inspect anyway. That inspection connects the first group to the line rule instead of treating twelve moves as one unexplained instruction for every L.
A dot has no upward yellow edge stickers, so there is no line or L to aim initially. Choose any front with yellow up and white down. In the Dot example, one complete group produces yellow at front and right, with blue at back and red at left. This is an L, but it is not the required back-left L. A U2 setup moves its two yellow edge stickers to back and left. Only after that adjustment should you apply the L rule and then recognize the resulting line.
This dot trace explains a common failure of counting repetitions. Three applications are enough along the taught case route, but not by blindly keeping the same setup after every group. The first group gives you information that was absent at the dot. You must read that information and orient the new shape. Write the trace as dot, front-right L, setup U2, back-left L, left-right line, cross. The shape names describe observed states. They do not claim every dot has identical corners or side-color matches along the route.
Do not confuse a setup U turn with a turn inside the algorithm. In F R U R' U' F', the U and U' belong to the fixed six-move sequence and must both occur. A setup U or U2 is an extra action before the next F, chosen from the newly inspected pattern. A vertical regrip changes positional names together. Both can set a yellow-cross shape, but their exact effect on side-color matches differs. That matters next lesson, where matched edges must stay matched during regripping.
The lower-layer preservation statement also has a boundary. This algorithm returns the completed lower layers after all six moves, while upper corners may change. It does not preserve every solved sticker after each individual turn, and it does not promise to keep a cross if you apply it unnecessarily. Once the cross exists, the action is to stop and inspect. An algorithm is not beneficial merely because it appears here. Its useful effect depends on an unfinished checkpoint, the correct entry conditions, and the stated shape setup.
F R U R' U' F'
In the demonstration below, choose Horizontal line and pause playback before following it. Reset returns that selected demonstration to its own start. Use Next step to inspect the intermediate states described above, particularly the state just before F'. The net records completed turns, while the solid cube can show motion between them. Wait for completion before comparing sticker squares. You can read the moves without animation. Neither playback speed nor how quickly you press Next step changes the six legal turns or the stage's stopping condition.
Now use the independent practice cube and select Horizontal line there as well. Matching the preset name does not link the two cubes. Predict which two upper edge squares are yellow before pressing a face button. Keep the recall cue closed and enter the six moves from memory, waiting for each animated turn to finish. Check my progress tests without moving pieces. A yellow cross with damaged lower layers is insufficient. Inspect those layers yourself as well, so the feedback confirms your reading rather than replacing it.
| Observation point | Inspect | Decision |
|---|---|---|
| Before the first F | Lower layers and four U edge squares | Establish entry condition and shape setup |
| After F R U R' U' | Move count, not a new shape case | Finish the required F' |
| After all six moves | Four U edge squares and lower layers | Stop at cross; otherwise set the new shape |
A useful contrasting attempt starts from that same practice preset with an extra U. You changed the line to front-back. Before doing anything else, identify the wrong setup in the net. Undo last turn returns the original prepared line; alternatively another appropriate U turn can establish a left-right line. Restart this attempt removes the whole practice history and restores the preset. These controls let you distinguish a recognition error from forgetting a move. Do not keep executing the sequence simply because a previous attempt from the preset succeeded.
Select Back-left L for another independent attempt. Before moving, state that one group should produce a line, not necessarily complete this stage. After six moves, inspect all four upper edge squares and choose whether a setup is needed. Complete the next group only after making that decision. Then select Dot and predict the first result before checking it. Changing presets tests retrieval of the appropriate case rule. Repeating the line preset alone would leave the L and dot setup decisions untested, even if the button sequence became easy to remember.
For a physical cube, transfer the same decisions rather than copying the practice turn history. Confirm your own lower layers, choose a front, and name your own upper edge pattern. If it differs from the display, the display's next move need not be yours. Hold the cube with yellow up and align the moving layer before each gentle turn. You may inspect hidden stickers between complete groups. A screen shows intended piece movement, but cannot verify your cube's colors, condition, grip, or whether you turned the intended layer.
| Edge-only pattern | Setup before F | After the group |
|---|---|---|
| Dot | Any front, yellow up | Inspect the resulting L and set it |
| Two adjacent yellow edges | Yellow at back and left | Inspect the resulting line |
| Two opposite yellow edges | Yellow at left and right | Check for the cross |
| Four yellow edges | Do not start another group | Verify lower layers, then continue to edge matches |
Finish when four yellow edge stickers surround the yellow center and the bottom two layers still match every center. Leave corner orientation and yellow-edge side matches for their later stages. Before continuing, close the cue and say the full decision without reading it, including the line and L setups and the command to inspect after a complete group. If you need the cue, use it and try a fresh prepared attempt afterward. Independent recognition and correct execution provide evidence; a fixed repetition count does not guarantee later recall.
Prepared states isolate one task. Some examples happen to finish the whole cube; on a general scramble, stop at the stated checkpoint and continue with the next unfinished step.
Ignore corners. Hold the two yellow edge stickers at left and right.
Next: F. front face: clockwise quarter turn, viewed directly from outside that face. Completed 0 of 6 moves.
FRUR'U'F'
Sticker letters are colors: W white, Y yellow, G green, B blue, R red, O orange. Face names are positions: U top, D bottom, F front, B back, R right, L left. Read B and R in context.
The net shows the last completed turn; the solid view shows the turn in progress. Presets replace the starting state and reset playback. Reset keeps the selected example. Do not copy an autoplay demonstration onto your cube unless your starting state and grip match. Use manual steps for following along.
Start from a prepared state. These controls change this practice cube only. They do not control the demonstration above or your physical cube. Goal: Make the yellow edge cross.
0 moves in this attempt. Limit 500; undo or restart if reached.
F R U R' U' F'
A cue is help, not a failure. After using it, restart the prepared state and attempt the same task without reopening it.
Sticker letters are colors: W white, Y yellow, G green, B blue, R red, O orange. Face names are positions: U top, D bottom, F front, B back, R right, L left. Read B and R in context.
Face turns and whole-cube regrips animate in the solid view; the net updates when the turn finishes. Reduced motion shows the result immediately. Wait for a turn to finish before starting another. Undo can cancel the current turn. A new preset or Restart cancels motion, replaces the entire attempt and clears its history. Undo reverses only the last practice turn. Check does not move pieces or reveal an automatic solution. State is local to this page and is not saved after reload.
The two yellow top corners form a diagonal, but no top edge sticker is yellow. Which case is it?
Corners do not participate in this recognition test.
It is the dot case. The yellow center does not count as an edge either. Apply the six-move sequence, then recognize the new edge-only pattern.
Two yellow edges point toward the front and back. What setup is needed?
The algorithm’s line case is horizontal in the top view.
Turn U by a quarter turn, or regrip around the vertical axis, so the yellow edges occupy left and right. Then use the six-move sequence. Do not run the line case while holding it front-back.
The explanations, simulator, and diagrams are original. These references support standard notation and beginner procedures. The course keeps white down, including the final twisting stage. Do not mix its final sequence with a tutorial that flips the cube over.
These examples use states produced by legal turns. The simulator has no sticker-painting input and does not diagnose physically twisted, reassembled, or damaged cubes. Successful model checks do not establish physical-device usability or long-term recall.