What do the question-mark tiles mean?

They are covered parts of the block. Wait for the target route to expose a removable colored face instead of tapping the cover early.

Why are green and pink cubes still visible at the end?

The block has collapsed into separated pieces, but those pieces still belong to the active target sequence until the checkmark appears.

Cube Tap Sort level guide

hard 12 colors

Open Level 28's covered color block from blue and yellow, then manage the collapsing board through the final green and pink pieces.

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From the exposed front faces, clear blue 10 and yellow 1; leave the question-mark cover untouched.
After the block re-presents automatically, follow the green/pink and red/orange groups on the separated pieces.
Inside the separated block, take gray from the exposed support and cyan from the newly open inner layer; leave any rear match behind the cover.
During the collapse, preserve buffer capacity for the current green/pink phase instead of using a question-mark tile as temporary storage.
Clear the final green/pink pieces from the separated lower and side cubes after their target boxes appear, then wait for WELL DONE.

Colors in this level:

Blue, Yellow, Green, Pink, Red, Orange, Gray, Cyan, Purple, Lavender, Peach, Lime

Take blue 10 and yellow 1 from the exposed front faces, not the brown question-mark tiles.
After the block shifts automatically, follow the green/pink and red/orange targets on the open pieces.
Keep buffer space available for the separated end cubes; question marks are cover, not a shortcut target.

Board notes 5 details

Layout: The opening board is a dense multicolored block with orange-brown question-mark cover tiles. Blue 10 and yellow 1 are active, and the buffer row is empty.
Goal: Advance through green, pink, red, orange, gray, and cyan before clearing the final separated green/pink pieces.
Opening: Clear the exposed blue 10 and yellow 1 groups first.
Danger Zone: Question-mark tiles conceal later faces, and the final green/pink cubes can be scattered after the main block collapses.
Mechanics: A covered dense block re-presents automatically as separated colored cubes while the target row advances; the source does not introduce a new manual swipe. Question-mark tiles remain cover throughout the collapse.

What do the question-mark tiles mean?
They are covered parts of the block. Wait for the target route to expose a removable colored face instead of tapping the cover early.
Why are green and pink cubes still visible at the end?
The block has collapsed into separated pieces, but those pieces still belong to the active target sequence until the checkmark appears.