Hostiles are advancing down the canyon road toward your core. Build and upgrade towers along the flanks, hold the line through 20 waves, and don't let them reach the gate.
01 Buy a tower from the Armory, then click a green build cell to place it.
02 Click a placed tower to upgrade or sell it for 70% back.
03 Frost slows enemies, Cannon splashes, Gun shreds single targets.
04 Auto-start & 2× speed keep the pressure coming. Survive to win.