How many balls does the Level 504 solution fire?

It fires 21 of the starting 29 balls and keeps 8.

What is the first weak point?

Break the upper-right brown-cylinder brace to spill the cage load.

Once the upper-right brace opens, the brown and navy cylinders roll out under gravity and leave the cyan columns exposed.

Smash Fest! level guide

expert Target: 21 moves 5 colors

Open the upper-right cylinder cage, spill its brown and navy load, then break the cyan base and orange roof with 21 fired balls.

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Strike the upper-right brown-cylinder brace to open the cage.
Break the next exposed right support and let the brown and navy cylinders spill away.
Remove the remaining cage supports while avoiding round pieces that are still rolling.
Shoot through the cyan base columns after the heavy middle has emptied.
Wait for the orange roof crates to settle into a low row on the two blue rails.
Break the orange crates from the leaning outside edge toward the center.
Clear both stationary blue rail sections after the orange row is gone; the clear leaves 8 balls.

Colors in this level:

Brown, Navy, Cyan, Orange, Blue

Opening on the cyan base leaves the heavy cylinder cage balanced above it.
Chasing a brown or navy cylinder wastes a ball while gravity is already carrying it off.

Open the upper-right brown brace before touching the cyan base.
Wait for both brown and navy cylinders to roll away from the tower.
After the base breaks, clear the orange row before targeting the two blue rails.

Board notes 5 details

Layout: A narrow tower stacks orange star crates over a brown-cylinder cage filled with navy round pieces, all resting on thick cyan ice columns and two blue horizontal support rails.
Goal: Empty the cylinder cage, break the cyan base, remove the settled orange-crate row, and clear both blue support rails.
Opening: Strike the upper-right brown-cylinder brace twice so that side opens and the navy and brown pieces spill out.
Danger Zone: The cyan base is a poor first target while the loaded cage stands; do not spend shots on round pieces that are rolling away.
Mechanics: A loaded cage release precedes a cyan base-column collapse, an orange-crate row, and a two-rail finish.

How many balls does the Level 504 solution fire?
It fires 21 of the starting 29 balls and keeps 8.
What is the first weak point?
Break the upper-right brown-cylinder brace to spill the cage load.
Why are direct shots at the round cage pieces unnecessary?
Once the upper-right brace opens, the brown and navy cylinders roll out under gravity and leave the cyan columns exposed.