Drag left and right to move the cannon. It fires by itself into the lane it is in.
The middle lane is the fight lane: enemies march down it and your soldiers battle them there. If they cross your sandbag line you lose HP. Card lanes send cards toward you. Touch a card with a soldier to apply it to your whole army: ×2 ×3 ×5 +10 are good, −10 ÷2 are bad. Cards that pass you do nothing.
The prize lane sends a crate that needs many hits. Crack it to unlock new weapons and soldier types, or grab a bonus.
Above the lanes the field opens up: gates, walls, and the red bases. Destroy all bases to win. Keys 1 / 2 deploy champions.