Absolute Zero (BTD6)

"Ability is so cold it freezes all regular Bloons for longer, including White, Zebra, and Camo, slows MOAB-class longer, and greatly increases the attack speed of all Ice Monkeys for the duration."

- In-game description

Absolute Zero is the fifth and final upgrade of Path 2 for the Ice Monkey in BTD6. Unlike in BTD5, Absolute Zero's attacks are based upon the Arctic Wind upgrade instead of Ice Shards. Compared to the Absolute Zero's previous upgrade, Snowstorm, this upgrade comes with a much more powerful freezing ability that freezes and damages all bloon types for a full 10 seconds, and activating the Absolute Zero ability grants all Ice Monkeys on screen with +50% more attack speed for 10 seconds, and its ability cooldown is 20 seconds instead of 30 seconds. With this upgrade, there is no initial cooldown.

Additionally, its slowdown aura slows bloons by 60% instead of 50%, its main attack can freeze up to 300 bloons instead of 100, it has +10 increased range compared to Snowstorm for a total of 40 units, it can directly attack MOAB-class bloons (but not freeze them), and all its freezing attacks can penetrate 4 layers instead of 2. When crosspathed with Permafrost, every attack to MOAB-class bloons will apply a 25% speed reduction on hit (including with the ability).

It costs $17,000 on Easy, $20,000 on Medium, $21,600 on Hard, and $24,000 on Impoppable.

Summary
Absolute Zero has a large slow aura that allows it to act as decent bloon support. Its ability can freeze MOAB-class bloons for a respectable amount of time, reducing their speed to a near halt temporarily. In addition, the large range of the tower can allow for a larger amount of land towers to be placed on water.

Because the Absolute Zero improves its range, potency of its slowdown aura, and pierce, it is essentially a stronger version of Snowstorm and Arctic Wind, however considerably more expensive than many other options in its roles (e.g. Bloon Impact for bloon support and Bloon Sabotage for global slowing), and even faces competition from its own predecessors. The special attack speed buffs for Ice Monkeys with the Absolute Zero ability can be useful, but this one benefit remains limited to niche strategies involving heavy Ice Monkey defenses.

Tips

 * With Permafrost crosspath, Absolute Zero's can apply a permanent slow effect (including the ability); however, Larger Radius and Re-Freeze enables Absolute Zero to permanently keep bloons in place and have larger range. Both are acceptable crosspaths depending on the needs of your defense.
 * As Absolute Zero is much more powerful in Bloons TD 6, it can freeze MOAB-Class Bloons for a short time, slowing them down by an extreme amount. This is especially useful versus DDTs.
 * Even though the 2.0 update buff allowed Snowstorm to freeze MOAB-class, although for a much shorter time, the Absolute Zero upgrade is more useful because the slow effect lasts much longer. Also, Absolute Zero doesn't need crosspathing to affect Leads; there was a secret Version 25.0 nerf to Snowstorm that prevents its ability to affect Lead without Cold Snap (previously named Metal Freeze) or other lead-popping power.
 * The freeze effect is shorter than Bloon Sabotage, but it gives a much better speed reduction than Bloon Sabotage's 50%. This may come in useful on short rounds. On the other hand, Bloon Sabotage can slow entering bloons but Absolute Zero cannot.
 * The Ice Monkey speed buff effect works well alongside the other Tier 5 Ice Monkeys. If possible, set up Super Brittle and Icicle Impale for maximum effect.
 * Do note that MOAB-class Bloons affected by the ability count as frozen, so plan accordingly.
 * There is no initial cooldown for the Absolute Zero. Freely buy, use the ability, and sell at will, but keep an eye out on remaining money.
 * While external buffs to range will increase the size of the visual effect of Absolute Zero, the hitbox of the ice platform won't increase (although the Larger Radius upgrade will increase the platform's hitbox).

Extra Notes (Version History)

 * Although not stated in the Version 23.0 patch notes, Absolute Zero had gained a 20-second initial cooldown for its ability. This addition of an initial cooldown was not reverted in Version 23.1 or Version 23.2. It was, however, in Version 25.0.

Sounds
When activating Absolute Zero Ability:
 * [Blizzard howling]

Trivia

 * The previous upgrade, Snowstorm, is a weaker variation of the BTD5 Absolute Zero, being unable to fully freeze White and Zebra Bloons, however this upgrade is better being able to freeze everything excluding the B.A.D., including M.O.A.B-Class Bloons.
 * Absolute Zero formerly joined Super Brittle as the Tier-5 upgrades with the smallest range (besides Sniper, Heli, Ace, Mortar, whose displayed range simply doesn't count as "range"), but this was no longer the case in Version 7.0, since Absolute Zero now has double the range of a normal Ice Monkey.
 * Unlike Bloons TD Battles Mobile, Absolute Zero in BTD6 received price decreases and mechanic buffs instead of price increases.
 * After Version 8.0, when all farming-only abilities (including Tier 5 upgrades in this case) are required to undergo a full initial cooldown duration, the Absolute Zero ability is one of four abilities that, when bought, has the cooldown up immediately. The others are Pirate Lord, MOAB Eliminator, and Total Transformation.
 * Between Version 23.0 and 25.0, this was not true. In Version 23.0 it had half initial cooldown, while 23.1 buffed AZ ability's main cooldown to match Snowstorm, changing AZ's initial cooldown to one-third.
 * In the BTD6 subreddit, there was a recurring meme since around the release of Version 8.0 whereby various users suggested a buff to the freezing of its main attack and ability from 2 to 5, writing "Absolute Zero freezes more (2 → 5)".
 * In Version 17.0, its freeze penetration has been buffed, but only from 2 layers to 4.
 * Although Ninja Kiwi claimed the attack speed buff during ability to be +50%, to which is true, they did not use correct attack speed calculations for Path 2 Bomb Shooter buffs.
 * The attack speed buff is displayed on affected Ice Monkeys with a unique icon, different to the one used for the ability itself. Simiarly to the icons for the other Tier 5 upgrades, it depicts a single M.O.A.B. being frozen.
 * In BTD6, Absolute Zero is the first upgrade in alphabetical order.
 * In real life, the absolute zero is the lowest limit of the thermodynamic temperature scale, with a temperature of zero kelvins or negative 273.15 °C.