How many balls does the Level 560 clear use?

The verified walkthrough fires 23 of 29 balls and leaves 6.

Why open the upper-right side first?

That side removes the roof support and spills the purple cans without trapping them above the cyan shelves.

The last white target block and a short red post on the platform usually survive after the roof has fallen.

Smash Fest! level guide

expert Target: 23 moves 6 colors

Break the upper-right roof step, spill the purple cans, and finish the lower red posts in 23 shots.

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Hit the upper-right purple cluster and the cyan block beneath it so the top step loses its right support.
Continue clearing the exposed upper-right shelf until the top purple cans and red blocks spill away from the board.
Wait for the falling roof pieces to settle, then attack the lower-right red post and the cyan shelf that still spans the middle.
Strip the middle shelves from right to left, removing the leaning white target block and the purple cans that land on the platform.
Clear the remaining center-left cyan beam and the tall red post that still stands on the base.
Finish the last white target block and short red star column on the platform; leave 6 balls.

Colors in this level:

Purple, Cyan, Red, White, Blue, Gold

Keeping your aim on loose purple cans after the roof has already started falling.
Ignoring the lower red posts until the platform is crowded with shelves and cans.

Board notes 5 details

Layout: A tiered cyan-and-purple castle sits over a lower row of red star posts and white panels, with purple cans packed into the roof and side steps.
Goal: Open the upper-right roof, clear the cyan shelves, and remove the final white target block plus short red post from the platform.
Opening: Attack the upper-right purple cluster and the cyan shelf below it so the top step loses its right support first.
Danger Zone: Chasing top purple debris wastes balls because the real late blockers are the lower red posts and the white target block leaning against the shelf.
Mechanics: This stepped shelf collapse solves by stripping the upper-right roof and then dismantling the middle cyan beams and lower posts in order.

How many balls does the Level 560 clear use?
The verified walkthrough fires 23 of 29 balls and leaves 6.
Why open the upper-right side first?
That side removes the roof support and spills the purple cans without trapping them above the cyan shelves.
What usually remains at the end?
The last white target block and a short red post on the platform usually survive after the roof has fallen.