How many balls does the recorded Level 521 solution use?

It fires 14 of the starting 24 balls and finishes with 10 remaining.

Where should the first shot land?

Hit the lower-right brace beside the lowest cyan beam, then work upward along that same seam.

The long cyan floors keep rotating and sliding after the impact, often clearing several pieces without another shot.

Smash Fest! level guide

hard Target: 14 moves 5 colors

Open the right seam of the broad cyan-and-star-crate wall, let its long floors slide out, and clear the low debris with 14 fired balls.

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Strike the lower-right star-crate and gray-blue brace beside the lowest cyan floor.
Continue up the exposed right edge, breaking the orange target blocks that pin the cyan floors.
Pause as the right wall sheds blocks and the first long cyan beam rotates toward the sand.
Hit the exposed right ends of the middle cyan beams instead of their protected centers.
Break the remaining right-side star crates until the upper floors lean and fold to the right.
Wait for the cyan beams, orange blocks, and loose gray-blue pieces to finish sliding.
Clear the stationary low star-crate row and the last cyan or gray-blue piece; 10 balls remain.

Colors in this level:

Cyan, Red, Orange, Gray, Blue

Firing through the middle of a cyan bar while both ends are framed leaves the wall supported.
Chasing a beam already sliding off the right edge spends a ball on debris gravity will remove.

Board notes 5 details

Layout: Long cyan beams alternate with red-orange star-crate rows inside a wide frame of gray-blue caps and orange target blocks.
Goal: Release every cyan floor from the right, collapse the wall, and remove the stationary low crates and gray-blue pieces.
Opening: Strike the lower-right brace beside the lowest cyan beam, then continue upward along the exposed right seam.
Danger Zone: Center hits waste balls while both ends of the cyan floors remain boxed into the crate frame.
Mechanics: A right-edge shell opening turns the layered wall into a multi-floor slide followed by low-platform cleanup.

How many balls does the recorded Level 521 solution use?
It fires 14 of the starting 24 balls and finishes with 10 remaining.
Where should the first shot land?
Hit the lower-right brace beside the lowest cyan beam, then work upward along that same seam.
Why should I wait after the right wall opens?
The long cyan floors keep rotating and sliding after the impact, often clearing several pieces without another shot.