Which cover opens first in Block Out Level 721?

The tall left 3-cover opens first. At that reveal, the short top and broad upper-right covers are separate and both visibly show 9.

What moves first after the left cover opens?

Pull the newly revealed red L into center, then slide the pink horizontal right so the cyan bar, green L and yellow/orange stack can separate.

Block Out level guide

expert 8 colors

Level 721 takes a left 3-cover to zero while separate top and upper-right counters remain at 9; preserve the center shelf through both later reveals.

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Send the lower-right green square out, then remove the accessible orange rectangles; these first exits start reducing the left 3-cover and both separate 18-counters.
Move the purple vertical to its matching side exit and turn the framed yellow/pink L pieces through the bottom pocket without occupying the outlined shelf.
Complete the third left-cover trigger: the tall cover reaches 0 while the short top and broad upper-right covers each visibly remain at 9.
Pull the newly revealed red L into center first, then slide the revealed pink horizontal right to release the cyan horizontal, green L and yellow/orange stack.
Send the left reveal's cyan/red bars, green blocks and yellow/orange groups through matching exits one at a time, clearing each bar from the shelf after crossing.
Track the short top and broad upper-right badges separately as those real exits reduce their visible states from 9 through 1.
Clear the final exposed pink/yellow pieces at the 1-to-0 burst; both late covers show 0 before their top-band and right-grid contents appear.
Pull the revealed purple vertical down into center first, then remove the upper red group, pink blocks and cyan/blue long bars before either framed L.
Send the long pink horizontal and remaining red bar out, followed by the small green squares and green vertical.
Turn the framed green L through the empty center last; it leaves immediately before the board clears and the Level 721 PERFECT card appears.

Colors in this level:

Orange, Yellow, Red, Purple, Green, Pink, Cyan, Blue

Treating the two 18-counters as one cover and missing that the left cover is already 0 while both still show 9.
Parking a long cyan/red bar across the center shelf before either late cover reveals.

Read all three cover badges separately; the first reveal occurs with two counters still at 9.
Use the center shelf only for crossing pieces and move every long bar clear after it passes.

Board notes 5 details

Layout: Three separate purple-faced covers marked 3, 18 and 18 fill an oval board above a compact lower pocket of orange, yellow, red, purple and green pieces plus framed yellow/pink L shapes.
Goal: Open the left cover with both remaining badges still at 9, drain its reveal, then track the short top and broad upper-right counters independently into the full-board refill.
Opening: Remove the lower-right green square and bottom orange rectangles, move the purple vertical out, and turn the framed L pieces without occupying the four-cell shelf.
Danger Zone: The outlined center cells and row above are the sole transfer corridor; a long cyan/red bar or framed L parked there blocks the next revealed object.
Mechanics: The left cover starts at 3 and opens while separate top and upper-right covers that start at 18 still show 9; the late covers retain their own visible badges.

Which cover opens first in Block Out Level 721?
The tall left 3-cover opens first. At that reveal, the short top and broad upper-right covers are separate and both visibly show 9.
What moves first after the left cover opens?
Pull the newly revealed red L into center, then slide the pink horizontal right so the cyan bar, green L and yellow/orange stack can separate.