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24 Portable Lakes at Dark Castle

Stacking Portable Lakes in order to test the heights of the castle and the forest in Dark Castle.

Height Testing is a newly-developed concept in BTD6. It is mainly about testing the heights of certain obstacles or monkeys in-game and measured using custom-made units such as Portable Lakes, Carrier Flagship, or Bloon Exclusion Zone.


The origin of height testing in BTD6 is now difficult or even impossible to find. The most common and well-known first ever photo evidence is a video of ISAB, a Bloons TD series YouTuber. This became the inspiration of other height testers.

Later, a post on Reddit listed the heights of all the obstacles in BTD6 and also shouted out a certain other height testers.


A height test includes the followings:

Height test subject[]

The subject you want to test, commonly an in-game obstacle.

Attack height[]

The height where the Height tester attacks. For example, a 0-0-0 Super Monkey's attack height is lower than a 1-0-0 Super Monkey's because the former one attack using his hand (not to mention at the shoulder level) while the latter one attacks using his eyes.

Height tester[]

A height tester is the tower to test if the height of the plane it is on is higher, lower or equal to the height test subject. Because the attack height of a tower varies with the tower's upgrades or kinds, it is better to use different towers while testing to minimize the error caused by the difference between the attack height of the tower and the height of the tower itself. A height tester is commonly the 0-0-0 Sniper Monkey because he has full map range and somehow taller than the Full Auto Rifle. Any tier or crosspathed Super Monkey is also suggested as it also has a large range and its attack height varies as the upgrades of him varies.

Height stacker[]

The height stacker is the tower to increase the height of the height tester. Commonly Portable Lakes or Carrier Flagship.

Height unit[]

The height unit is a custom-made unit of measuring the height of the height test subject, height test, attack height of the height tester or the height stacker, e.g. PL for Portable Lakes.


Here is a common step of height testing if the height test subject is an in-game obstacle:

  1. Choose the heights test subject.
  2. Place down a height stacker.
  3. Place the height tester on top of it to see if it can shoot over the height test subject.
  4. Repeat step 2&3 until the height tester can shoot over the height test subject.
  5. The height of the total used height stacker(s) will be the height of the height test subject.

Here is an inaccurate step of height testing if the height test subject is an amphibious in-game tower.

  1. Place it at the ground part of Flooded Valley.
  2. Open the valve to let the water flood in.
  3. Compare its rest-over height to the dam (whose height is tested to be 2PL).

Here is a common solution if the tower is a land tower.

  1. Place the tower on the land area of Flooded Valley.
  2. Use bugs to move it to the other side.
  3. Compare its rest-over height to the dam (whose height is tested to be 2PL).


See also[]

  • The attack behavior Tall/Height Tall