You can only hit boxes on the bottom row.
If a box is destroyed, the boxes above it will fall down.
If the numbers on adjacent boxes form a sequence starting with one, all of the boxes in that sequence are destroyed.
Which boxes do you need to hit to destroy them all with just two cannonballs?
Touch a cannon to fire it at the corresponding box.
The answer is as follows.
1. Shot to destroy the 4.
2. Shot to destroy the 5.