2TC



"Complete a game in CHIMPS Difficulty with only 2 monkey towers"

- BTD6

2TC is an achievement in BTD6, introduced in Version 12.0. It can be achieved by completing CHIMPS Mode with only two towers. Earning this achievement will reward 2 Monkey Knowledge Points and a 0-4-0 Wizard Monkey. The achievement remains invisible until the achievement is completed, as it is one of many hidden achievements in the game.

Strategy
2TC requires precise strategy by selecting two different towers that can beat all stages of the game. Firstly, the first tower (and therefore starting tower) must be purchasable in the first round with $650. Secondly, the second tower must be strong enough in combination with the first tower to combat the early-game weaknesses and possess enough firepower with its intermediate tiers and final tiers to counter the mid-game and late-game. Usually, the late-game will be the most difficult part of this challenge, but occasionally the beginning can be very difficult too. And lastly, 2TC should be done on a Beginner Map for the best results; 2TC on Intermediate Maps is entirely possible but never recommended.

The first roadblock comes from choosing the right starting tower, which for $650 cannot offer much. Getting through the early-game can also be an issue, but not as problematic as the first few rounds. Beating key rounds such as Round 24's Camo Green, Round 25's Purples, Round 28's Leads, and Round 40's MOAB are among many roadblocks during the early-game.

The second roadblock is getting through the mid-game with the intermediate tiers. Some combos may be very powerful in combination once their highest tiers are afforded but cannot be practically done due to both towers having insufficient firepower to handle the mid-game prior to those higher tiers. Most of the time, this specific problem comes from attempting to beat Round 63, but sometimes Round 76 can be the source of the trouble. For purposes of completing the achievement and not for trying to challenge oneself in special 2TC challenges, assume non-hero towers are bought to their maximum as soon as possible and heroes are never manually upgraded until the other non-hero tower is max tier.

The third and final roadblock is affording those highest tiers of tower and using the final duo to beat Rounds 81 to 100 without need of additional support. Round 98 and Round 99 are normally the most difficult aspects of 2TC for almost all combos due to providing two distinct extremes; Round 98 requires effective counters to hyperdense rounds with Fortified BFBs and ZOMGs, and Round 99 requires quickly damaging Fortified DDTs as soon as they arrive, which combined provide the majority of the roadblocks in 2TC. Ability timing is very important, if the duo contains activated abilities. Round 100 is the final round to watch out for looking ahead, as the BAD is full of health and needs to be destroyed with pure single-target damage.

Certain heroes and Tier 5 upgrades are designed in such the way that makes them perfect for 2TC. Sauda is notably the single-best 2TC hero in the game, followed by Captain Churchill. As for Tier 5 upgrades, Prince of Darkness, Wizard Lord Phoenix, the 5-2-0 Sky Shredder, the 5-2-0 Apache Prime, and the 5-2-0 Ray of Doom are among the most suitable options in 2TC for many reasons, many of which have combos of their own when combined with many other powerful towers in the game. For purposes of completing the achievement, 2TC combos with Prince Of Darkness plus any tower with sufficient MOAB-class damage tend to be the easiest to execute, such as PoD + MAD or PoD + RoD.

Tips

 * The community-made record of 2TC completions can be found here. It can be useful to refer to if attempting this challenge.
 * For the best results, attempt this achievement on the map Logs. The sheer length of the map and the various wide corners make it very handy to catch bloons partway through the entire track. This is especially the case for Rounds 95, 98, and 99.
 * The easiest 2TC combos are usually those with Sauda. Some of these combos are very easy to pull off, with the easiest being Sauda + Apache Prime. Some ability timings may be necessary to destroy the later rounds, but other than that it should be easy to do.
 * 0-5-2 Wizard Lord Phoenix + 5-2-0 Apache Prime is one of the easier combos outside of Sauda combos. Apache Prime will shred most of the bloons in the game quite easily, while Wizard Lord Phoenix can deal with any nasty blimp rushes or DDTs easily. The only difficult rounds include the transition from Round 98 to 99; be sure to have the Wizard Lord Phoenix ability recharged before fully completing Round 98.
 * 0-2-5 Prince of Darkness + 5-2-0 Apache Prime is another easy combo after Prince of Darkness was buffed in Update 21.0. The only hard rounds are 98 and 99 but with micromangement they should be pretty easy.
 * 0-2-5 Prince of Darkness + 2-5-0 Carpet of Spikes is also a relatively easy combo. Start with 0-2-1 Wizard, and go for Spike Factory close to the Wizard. Upgrade towards 2-3-0 MOAB SHREDR and 0-2-4 Necromancer before Round 40. Get 0-2-5 Prince of Darkness and 2-5-0 Carpet of Spikes. Proper timing of the ability should be done with the Carpet of Spikes activated ability, specifically on either heavy rounds or high-HP rounds like Round 94, 96, 97, and 98, while the Prince of Darkness should clean up the rest easily.
 * 0-2-5 Prince of Darkness + 5-0-2 Sky Shredder is on the easy end of the spectrum as well. The early game is a tad bit difficult but after getting a 0-2-4 Necromancer, followed by 3-0-0 Fighter Plane and 4-0-1 Operation: Dart Storm, finishing with 0-2-5 Prince of Darkness and 5-0-1 or 5-0-2 Sky Shredder. This technique only requires micromanagement in the early game, and only with the Wizard, implying the placements are ideal.
 * 0-2-5 Prince of Darkness + 5-2-0 Ray of Doom is another easy combo, but for the best results it should be done on Resort and not Logs. Place the Wizard on the top of the small square so that when upgraded to Wall of Fire it will land Walls of Fire on a convenient intersection. 0-1-0 Wizard should be bought first, firstly with 0-0-0. Upgrade to 0-2-0. Save up to Dartling Gunner and place it at the start of the track but as far up as possible. Lock the Dartling at the intersection near the end, but aim it slightly high. This placement utilises the bonus damage of the end point of the 4-0-0 Dartling Gunner. Upgrade 0-0-0 Dartling to 0-2-0 Dartling for the Camos and reliable purple-popping. Then get 0-2-2 Wizard and then 3-2-0 Laser Cannon. Afford 0-2-4 Necromancer and 4-2-0 Plasma Accelerator. Save money until affording Prince of Darkness. Then save up a long way towards Ray of Doom. It seems extremely expensive to go towards, but once Ray of Doom is afforded it is almost a guaranteed win as long as the Ray of Doom is targeted onto the right spot.
 * 5-0-2 Glaive Lord + 2-5-0 M.A.D is on the easy side of the 2TC spectrum, as long as you micro the Dartling Gunner during required times. Start of with a 1-0-2 boomerang, and save up for Dartling; Hydra Rocket Pods is required for camo leads. Then try to upgrade to Glaive Lord and then save up for MAD. Glaive Lord will pretty much solo until rounds 82-85, then get MAD and you're pretty much set. Micro a bit during rounds 98-99 and the victory should be there.

Specific loadouts
Most information here is mostly oriented for players wanting to attempt advanced 2TC combos, rather than focusing on earning the achievement.

Near-solo
"Near-solo" in this context refers to nearly soloing 2TC when given a tower that can counter obvious weaknesses.

There are a certain number of towers in 2TC combos that can solo all Camo Bloon rounds as long as it is given another tower to handle other bloons:
 * 2-5-0 Carpet of Spikes
 * 2-5-0 MAD (2-5-0 for the focused Rocket Storm)
 * 5-2-0 Sky Shredder

There are a certain number of towers in 2TC combos that can almost fully solo late-game when given a way to counter obvious weaknesses in earlier rounds:
 * Wizard Lord Phoenix requires Round 25 Purple popping power, enough Camo Purple popping power for Round 45, 48, and 95, and some support Midgame.
 * Ray of Doom requires Round 28 lead-popping and decent cleanup for beating Round 63.
 * Captain Churchill requires an early-game tower to solo pretty much the rest of the game.
 * Sauda is a special case because she can be started off in the early-game and can save up greatly while combined with other towers.
 * The Anti-Bloon requires a camo-detecting tower that also has a lead-popping option and a decent synergy with Tech Terror in the saveup before the final upgrade.

"Perfect" combos
"Perfect" combos are 2TC combos that synergize with each other so well that the combination of the two flawlessly beat all stages of the game.


 * Sauda + Wizard Lord Phoenix
 * Prince of Darkness + Ray of Doom (also called POD & ROD).
 * Prince of Darkness + M.A.D

Bugs

 * It used to be possible to complete the 2TC CHIMPS achievement by completing a Challenge Editor challenge with Round 1 to 1 CHIMPS Mode with only two towers. The same bug also affected other achievements that were released on Version 12.0. This bug was fixed in Version 12.1.
 * In version 12.1, there's a bug that prevents gaining this achievement by using a Wizard Lord Phoenix (x-5-x Wizard) as one of the 2 towers. This was fixed as of Version 17.0.
 * This bug was caused by the game registering the phoenix as a separate tower.

Version History
Many nerfs and buffs have affected the ability of certain tower combinations to accomplish 2TC.

Trivia

 * This achievement is based on a popular challenge on BTD6 reddit where players would only use two unique towers to beat CHIMPS mode, which is considered to be very hard as some combos need hours to complete which may require precise usage of ability and/or luck for the towers to hit the bloons.
 * The first recorded completion was 5-0-2 Energizer + 2-5-0 The Anti-Bloon in Version 2.1, when super ceramics gave extra cash. It became impossible due to the bugfix in 4.0, then became possible again in 25.0 and gained a downgrade from Energizer to Bloontonium Reactor at the same time.
 * The next recorded completion was in Version 8.0.
 * As of 13 March 2021, there are 296 2TC combos, ignoring crosspathing.
 * Sauda has been used in 112 unique combos, the most of any tower. The second-, third- and fourth-most-used towers are Churchill, with 49, Wizard Lord Phoenix, with 45, and Prince of Darkness, with 26.
 * In a single day on 16th December 2020, Captain Churchill gained 24 new 2TC consecutive combos with various towers, recorded in the BTD6 Index. One day before then, Captain Churchill had a combo with Monkey Pirates.
 * As of the Permaspike + Archmage combo (171st combo), which was achieved on 12th February 2021 (Link), all Tier 5 Wizard Monkeys have a 2TC with Apache Prime (9th latest, PoD), Sky Shredder (41st latest, Arch), Carrier Flagship (75th latest, PoD), Captain Churchill (84th latest, PoD), Tsar Bomba (87th latest, PoD, no longer possible), and M.A.D (120th latest, Arch).
 * With the completion of the Sauda + Plasma Monkey Fan Club combo, every possible maximum upgraded tower, excluding Heroes, the Sun Temple, Super Mines, and Legend of the Night have been used in at least one 2TC.
 * Benjamin, Gwendolin, and Striker Jones are the only heroes that don't have a 2TC done with them yet.
 * Pat Fusty was done with Wizard Lord Phoenix by using a Version 25.0 glitch related to his Rallying Roar giving normal damage type.
 * With the completion of the Sauda + Super Brittle combo, every type of tower (excluding Heroes) has been used in at least one 2TC, as Ice Monkey was the only non-hero tower type without a 2TC before that completion.
 * On 9th July 2021, the first completion of 1TC has been done, using Sauda to solo CHIMPS Mode on Resort. As a result, Sauda's 1TC completion has lead her to receive 33 associate 2TC combos, bringing her new total to 202 2TC combos. The added associated combos are:
 * Tier 0-2 Dart Monkey, Spike-O-Pult, Juggernaut, Triple Shot, Crossbow
 * Tier 0-2 Boomerang Monkey, Bionic Boomerang
 * Tier 0-2 Bomb Shooter, Really Big Bombs
 * Tier 0-2 Tack Shooter, Blade Shooter
 * Tier 0-2 Ice Monkey, Cryo Cannon
 * Tier 0-2 Monkey Ace, Bomber Ace
 * Tier 0-2 Wizard Monkey, Shimmer
 * Tier 0-2 Ninja Monkey, Double Shot, Bloonjitsu, Shinobi Tactics, Flash Bomb
 * Tier 0-2 Druid, Druid of the Jungle, Jungle's Bounty, Druid of Wrath, Poplust
 * Tier 0-2 Spike Factory, Long Life Spikes
 * Tier 0-2 Engineer Monkey, Cleansing Foam, Double Gun, Bloon Trap.