Start with 20 lives and a difficulty-based bank: Easy $350 · Normal $325 · Hard $300 · Expert $275. Added enemy health and tighter spacing ramp up across waves 1–5. Hard and Expert bosses are tougher. Build on empty cells, then send a wave. Survive 40 waves across eight maps. Waves 1–10 contain 20 enemies, 11–20 contain 25, 21–30 contain 30, and 31–40 contain 35. A boss takes one slot. Extra enemies share the existing wave bounty.
Eight unique towers, no tiers. Each starts at L1 and upgrades twice to L3. Attacking towers gain 40% damage per upgrade. Range at L2 / L3 is +16% / +32% of starting range; Frost gains +8% / +16% instead. Amplifier range is 45 / 52 / 60 at L1 / L2 / L3. Frost improves its slowing strength; Amplifiers boost damage by 20% / 30% / 40%. The strongest nearby Amplifier applies; they never stack. Sell towers for 75% of their investment.
Upgrade or expand? Upgrade strong positions for more damage. Build elsewhere to cover another route, or choose another tower to counter armor, crowds or immunity. The tower panel shows exact upgrade gains and color matchups.
PULSE LASER Fast single-target fire; strongest against green and blue.
CHAIN ARC Up to 3 enemies per shot, losing 20% damage each jump.
ROCKET LAUNCHER Long-range homing splash, strong against red.
PLASMA MORTAR Heavy area damage, strong against purple and grey; weak against blue.
FROST FIELD Slows up to 3 / 5 / 7 active targets by 52% / 62% / 72%. Purple is slow immune.
RAILGUN Heavy, slow, long-range shots for armored targets.
CORROSION TOWER 4 seconds of damage over time; refreshing does not stack it. Sealed Drones are immune to corrosion but still take direct damage.
AMPLIFIER Improves every attacking tower in range, without a target cap; cannot attack. Gold links and + markers identify boosted towers.
Bosses arrive on waves 10, 20, 30 and 40. Read their abilities and highlighted route before sending the wave. Ironclad has armor and slow resistance; Broodmother releases hatchlings; Phase Walker alternates its shield; Overlord enrages and summons escorts. Each boss kill awards money and a power cell.
Regular escapes cost 1 life and return to their entrance. Boss escapes cost 3 lives and leave permanently. Remaining escorts must still be cleared. No boss is immune to an entire tower’s damage.
Expert: regular waves alternate their main attack route (cyan dotted preview), with roughly 80% of enemies on one route. Armored Red, Purple Swarm, Blue Rush and Sealed Advance need different counters. Income is 10% below Easy and auto waves wait 10 seconds for planning. Selling still refunds 75%; keep useful coverage and move investments when the next route or counter changes.
All difficulties use the approved Easy economy: opening interest ends after wave 5, later cleared waves award $10, and a supply power cell grants $50. Normal uses the same bounties; Hard pays 5% less and Expert 10% less. From waves 6–15, Normal / Hard / Expert gradually reach +10% / +20% / +30% enemy and boss health versus Easy, with 5% / 10% / 15% shorter spawn intervals. Mixed waves begin at 25; Hard and Expert use three colors immediately, Normal reaches three at 31. Extra enemies and summons do not increase the advertised bounty.
Keys 1–8 select towers; arrows move the cursor; Enter places; U upgrades; P pauses; Space starts, pauses or resumes; Esc cancels. Auto waves wait 8 seconds before a boss and 5 before resistant enemies. Pause to plan.