Machine Cannon Bunker

Reload {2}{t}: Add 1 charge.
Precision Shot {t}: Remove 1 charge. Deal 3 damage to
1 attacking nonflying creature.
Salvo {t}: Remove 2 charges. Deal 3 damage across up
to 3 target attacking nonflying creatures.
Full Unload {t}: Remove 4 charges. Deal 3 damage to
up to 4 target attacking nonflying creatures.
MCB enters the battlefield with no charges.
MCB can store max 4 charges.
A huge wall of notthing but gun.