How many balls does the recorded Level 523 solution use?

It fires 23 of the starting 28 balls and finishes with 5.

Why start in the lower-right frame?

That corner supports the right shoulder of the gray diamond; opening it starts the core collapse.

Remove the shortened gray pedestal stack and the stationary orange target crates left along the platform.

Smash Fest! level guide

expert Target: 23 moves 5 colors

Release the dark-gray stepped diamond through its lower-right frame, break its pedestal, and clear the orange base with 23 fired balls.

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Break the lower-right orange star crates beside the gray diamond.
Remove the exposed right-side white-red cylinders and continue into the diamond's lower-right step.
Wait for the right shoulder of the gray mass and its surrounding frame to drop.
Strike the exposed lower gray blocks, shrinking the diamond from the bottom instead of shaving its top.
Open the remaining side-frame pieces as they become unsupported.
Break the narrow gray pedestal under the shortened core and let the upper blocks tumble.
Clear the low central gray stack and the stationary orange target crates across the platform.
Finish the separated edge crates and wait for the empty-platform clear; 5 balls remain.

Colors in this level:

Gray, Red, Orange, White, Blue

Shooting the top of the dark-gray diamond before opening a lower corner leaves its full weight supported.
Continuing to fire during the heavy-core drop sends balls into moving gray blocks instead of the pedestal.

Board notes 5 details

Layout: A heavy dark-gray stepped diamond fills a red-orange star-crate frame with white-red side cylinders and an orange target-block base.
Goal: Open the lower-right frame, drop the gray core, then remove the compact pedestal remnant and base-row crates.
Opening: Break the lower-right star crates and side cylinders so the diamond's right shoulder loses support.
Danger Zone: Direct hits on the broad gray face accomplish little while the orange frame still supports both lower corners.
Mechanics: A heavy-core release converts a framed stepped diamond into a compact pedestal cleanup.

How many balls does the recorded Level 523 solution use?
It fires 23 of the starting 28 balls and finishes with 5.
Why start in the lower-right frame?
That corner supports the right shoulder of the gray diamond; opening it starts the core collapse.
What is the late cleanup target?
Remove the shortened gray pedestal stack and the stationary orange target crates left along the platform.