Three enemy paths converge from the left side of the map. Build towers to destroy enemies before they reach the exit on the right. You start with 1,000 gold and 30 lives. Lose all lives and it's game over. Survive as many waves as you can.
Each tower can be upgraded twice (Lv1 → Lv2 → Lv3), then specialized into one of two unique branches. Towers take time to build (5–10s), so plan placements ahead of incoming waves. Towers have HP and can be damaged by Sappers — click a placed tower to see its stats, repair, upgrade, sell, or (after branching) buy a shield.
Power: All combat towers require power to operate. Build Power Plants to provide power to nearby towers. Unpowered towers cannot target or fire. Plan your Power Plant coverage to keep your defenses online!
After wave 12, enemies can spawn as elites with boosted stats and rewards.
Four global research tracks in the sidebar. Each has a branching structure: two linear tiers, then a branch choice (A or B) which unlocks two final sub-specializations. You can reach 4 nodes per track. Research takes time and costs scale steeply — plan these as long-term investments.
After specializing (branching) a tower, you can purchase a consumable shield for it. Shields absorb incoming damage before the tower's HP is touched. If the shield is partially damaged, you can recharge it for a prorated cost — you only pay for the missing portion.
After specializing a tower, you can overcharge it for a temporary +25% damage boost lasting 60 seconds. Overcharge costs 30% of the tower's invested gold (scaled by wave inflation), making it a significant late-game gold sink that rewards active management. You can re-apply it once it expires.
Gold comes from kills and wave-clear bonuses. Kill rewards decay slightly each wave (down to 50% minimum), and tower costs inflate by 2% per wave. Selling towers refunds 60% of their cost — don't be afraid to reposition. Research can improve sell rates.
Cryo towers at path convergence points are extremely valuable since they slow enemies from all three paths. Pair with Tesla or Nova for area coverage, and use Rail towers on long straight segments. Prioritize killing Healers and watch for Sappers chewing through undefended towers. Once towers are branched, invest in shields on your most exposed positions — they're consumable but can save a critical tower from Sapper fire.