Polyphemus

Map overview for strategy

Polyphemus has two lanes running at once. Bloons enter from both edges, circle the island, loop once around the eye and exit on the opposite side. The eye-shaped pond in the middle is the key to the whole map.

Towers in the eye get three buffs: 15% cheaper towers and upgrades, 17.6% faster attacks and camo detection. That makes it the best spot on the map for subs and boats. The downside: after every round ending in 5, the eye closes and everything inside stops working until you pay to reopen it.

How to handle the eye:

• Budget for it. Reopening is free up to round 15, then $500 for rounds 16 to 25, $1,000 for 26 to 35, rising by $500 every ten rounds. Through round 100 it adds up to $22,500. Rounds 76, 86 and 96 cost $3,500, $4,000 and $4,500 respectively.
• Turn off auto-start. The eye closing in the middle of a smooth game can surprise you. With auto-start off, you always have time to reopen it.
• Do not depend on the eye alone. Keep enough defence outside the eye to survive a round if you cannot afford to reopen it.
• Never put an Arctic Wind in the eye. When the eye closes, the Arctic Wind is disabled and every tower standing on its ice is force-sold.

The loop around the eye means towers in or near the pond see both lanes, which is another reason it is worth the cost.

Best towers

• Monkey Sub 2-0-4 (First Strike Capability) in the eye. The discount and attack speed buff make subs here far better than usual, and the eye gives them camo detection.
• Monkey Buccaneer 3-2-0 (Destroyer) in the eye for strong popping across both lanes.
• Beast Handler. The only tower that can get around the eye closing: water beasts whose range reaches the sea are moved into the ocean instead of being disabled. Experienced players also use Arctic Wind outside the eye to place Handlers in the pond and merge them with Handlers outside, which saves a lot of money on high-tier beasts.
• Ninja Monkey 4-0-1 with an Alchemist 4-2-0 on the grass near the eye.
• Glue Gunner 2-0-3 (MOAB Glue) near the loop around the eye.
• Mortar Monkey 0-2-4 (Shattering Shells) aimed at the loop around the eye.

Best heroes

• Admiral Brickell. The eye and the sea give her plenty of water towers to boost. Avoid placing her in the eye, where she would be disabled every ten rounds.
• Sauda. On the grass next to the eye she reaches both lanes as they loop.
• Obyn Greenfoot. Good with Ninjas and Alchemists on the grass.
• Psi. Unlimited range covers both lanes without line-of-sight issues.

Easy and Medium

Place a sub in the eye on round 1 and upgrade it to Advanced Intel. Add your hero on the grass next to the eye. The eye gives camo detection, so a sub in it handles round 24. Get lead popping by round 28 with Heat-tipped Darts. A Ballistic Missile sub handles round 40. Reopen the eye whenever it closes. On Medium, add Destroyers and an Alchemist for round 60.

Hard

1. A sub in the eye and your hero beside it from round 3.
2. Heat-tipped Darts by round 28 and a second sub.
3. A sub at 2-0-3 for round 40.
4. Destroyers, an Alchemist, a Glue Gunner and Shattering Shells by round 63.
5. Two or three First Strike subs in the eye for round 80, with cash set aside to reopen the eye after round 75.

CHIMPS

CHIMPS starts on round 6 with $650. The eye discount makes your money go further, but the reopening costs add up. A realistic plan:

1. Round 6: A Monkey Sub in the eye plus your hero (Sauda or Obyn) on the grass next to it, or just a sub and a Dart Monkey if your hero is expensive.
2. Rounds 7–20: The sub to 2-0-0, a second sub or a Buccaneer in the eye. Reopen the eye after round 15 ($500).
3. By round 23: camo is covered by the eye's buff for towers inside it.
4. By round 27: Heat-tipped Darts on a sub (2-0-2) for the leads on round 28. Reopen the eye for $1,000 after round 25.
5. Rounds 30–39: A sub to 2-0-3 for round 40.
6. Rounds 40–62: A Ninja 4-0-1 and an Alchemist 4-2-0 on the grass, a Destroyer in the eye, a sub toward 2-0-4 before round 60, and a Mortar 0-2-4 before round 63.
7. Rounds 63–80: Two more First Strike subs and a Glue Gunner 2-0-3. Save $3,500 for the reopening before round 76.
8. Rounds 81–100: More MOAB damage in the eye and on the grass. Reserve $4,000 for round 86 and $4,500 for round 96. Keep camo coverage outside the eye too, in case you ever cannot reopen it before round 95.

Impoppable

Same plan with higher prices and one life. Farms and Buccaneer income help pay for reopening the eye, and selling lets you move towers out of the eye if the costs get too high.

Other modes

• Military Only: subs and boats in the eye carry this mode.
• Half Cash: the reopening costs are not halved, so they weigh much more. Build more outside the eye.
• Deflation: you have no income, so decide early whether you can afford to keep the eye open.

Dangerous rounds on this map

• Round 24 (camo green): the eye gives camo detection, so towers inside it are covered. Towers outside need their own.
• Round 28 (leads): both lanes at once. Heat-tipped Darts on eye subs is the easiest answer.
• Round 40 (first MOAB): a Ballistic Missile sub in the eye is plenty.
• Round 63 (75 leads, 122 ceramics): two lanes of ceramics looping around the eye. Area damage on the loop is very effective.
• Round 76 (regrow ceramics): the eye closes after round 75 and costs $3,500 to reopen. If you cannot pay, you face this round without your eye towers.
• Round 78: a big mixed rush with camo ceramics.
• Round 95: camo leads and DDTs. The eye has been open since round 86 if you paid, but outside towers still need camo.
• Round 96 to 100: the eye closes again before round 96 and costs $4,500 to reopen. Round 98 brings fortified BFBs and ZOMGs, 99 fortified DDTs and 100 the BAD.

For a full walkthrough, see our videos on the BTD6 Master YouTube channel.

Frequently asked questions

What does the eye do on Polyphemus?

Towers in the eye-shaped pond get a 15% discount, 17.6% faster attacks and camo detection. The eye closes after every round ending in 5, disabling those towers until you pay to reopen it.

How much does it cost to reopen the eye on Polyphemus?

It is free until round 15, then $500 for rounds 16 to 25, rising by $500 every ten rounds. Keeping it open costs $14,000 through round 80 and $22,500 through round 100.

Why should you not put an Arctic Wind in the eye?

When the eye closes, the Arctic Wind is disabled and every tower placed on its ice is force-sold.

What is the best tower for Polyphemus?

Monkey Subs in the eye, thanks to the discount, attack speed and camo buffs. Beast Handlers are also great because their water beasts can escape the eye closing.

How do you beat Polyphemus on CHIMPS?

Build subs and boats in the eye, add a Ninja and Alchemist on the grass, and budget for the eye reopening costs, especially $3,500 before round 76 and $4,500 before round 96.