Three chapters, one collapse

The campaign runs sixty levels across three chapters — Zombie Outbreak, Mutated Hordes and Ground Zero — plus a hidden sixty-first, The Final Stand, at the core of Site 9. Each chapter introduces four new towers and a fresh set of things trying to get past them, and the story of the Toxiqa incident is told while you fight, in field dispatches and PA announcements. Stars gate the way forward: twenty-five open the mutations, fifty-five open Ground Zero.

Twelve towers, four per chapter

Every tower upgrades three times, and at the final tier it branches: pick a specialisation, not just a bigger number. Six targeting modes on every tower — first, last, strongest, weakest, support, shielded — decide what it shoots at. Sell one to reclaim resources when the wave composition changes and your plan no longer fits. The Supply Depot shoots nothing and generates gold instead.

Five damage types

Physical, chemical, electric, thermal and energy damage each meet per-enemy resistances, and occasionally a vulnerability worth building around. Damage after resistance is damage × (1 − resistance), so a negative resistance really does hurt more. Chemo zombies in hazmat suits shrug off your chemistry; tunnellers go underground where nothing can reach them.

When the line breaks

Strike, Freeze and Repair are active abilities on a cooldown, for the moment it all goes wrong. Call the next wave early for a thirty-percent gold bonus and fight two at once. Wave modifiers — Swift, Armored, Shielded, Regenerating, Frenzy and more — keep a well-drilled board honest.

Between runs

Every level pays Scrap, which buys nine permanent upgrades: range, damage, attack speed, starting gold and lives, ability cooldowns and the rest. Three difficulty modes change pacing, density and rewards, with stars tracked per difficulty. Clear a chapter and its Endless mode opens.

What it costs

Nothing. The whole game is here, start to finish, with no ads, no energy bars and no paywall. There is one optional in-app purchase — a coffee for the developer — and it unlocks nothing.