Why does an eighteen-space road still jam on Level 521?

Several center rows release large batches, so two unresolved colors can consume most of the perimeter at once.

Which colors should open the board?

Purple and pink clear first, followed by the exposed green and cyan destinations.

No. Its difficulty comes from layered rows and variable receiver sizes sharing one road.

Car Sort level guide

expert 9 colors

Car Sort Level 521 surrounds a layered central receiver grid with an eighteen-space road fed by two upper and three lower boxes.

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Send the exposed purple pair into its visible receiver.
Complete the first pink center group and route green from below.
Feed cyan into the newly exposed cyan column before upper orange moves.
Route the upper orange row and let its receiver drain.
Open the next center layer and complete green, pale-purple, and blue separately.
Pause at `14/18` until one long receiver exits.
Use the second upper box for purple and yellow only after both destinations appear.
Clear the late red horizontal rows before opening the final lower hidden stack.
Finish pink, green, pale-purple, cyan, and blue from the lower boxes.
Send the last red and yellow traffic, drain to zero, and confirm `Level Completed!`.

Colors in this level:

Purple, Pink, Green, Cyan, Orange, Pale-purple, Blue, Red, Yellow

Releasing a full hidden center row while another long batch is still circulating.
Blocking the right return before the lower green pair enters.
Adding yellow traffic at `16/18` without an exposed yellow receiver.

Board notes 5 details

Layout: Two upper towers and three lower towers feed long horizontal rows plus narrow vertical receivers inside a clockwise `18`-space rectangle.
Goal: Complete the center receivers in color phases, uncover hidden rows safely, and preserve the right return until the final red and yellow traffic.
Opening: Route exposed purple first, complete pink, then use open green and cyan destinations before releasing upper orange.
Danger Zone: A new long row at `14/18` or higher can strand red or yellow and block the lower green pair at the right return.
Mechanics: Variable-size center receivers and long hidden batches create capacity pressure without any countdown gate or numbered source.

Why does an eighteen-space road still jam on Level 521?
Several center rows release large batches, so two unresolved colors can consume most of the perimeter at once.
Which colors should open the board?
Purple and pink clear first, followed by the exposed green and cyan destinations.
Does Level 521 have a countdown gate?
No. Its difficulty comes from layered rows and variable receiver sizes sharing one road.