Your barrel sweeps from 0° to 90°. Fire when the arc lines up with the enemy cannon. Wait too long and the fuse fires for you.
Tap the field, click, or press Space to fire. One miss ends the run.
Each hit speeds up the barrel and shortens the aiming guide. Hills join at hit 2.
A direct hit loads an HE shell (blast hit counts). Every 4th hit loads AP, which flies through hills.