Heat-Tipped Darts

"Heat tipped darts allow popping of Frozen and Lead Bloons."

- In-game description

 (in-game as Heat-tipped Darts) is the second upgrade of Path 2 for the Monkey Sub in Bloons TD 6. It allows the Monkey Sub to pop Frozen and Lead Bloons. When used as a crosspath for the submerged Bloontonium Reactor, the Bloontonium Reactor deals +1 damage to Leads but not extra to Frozen Bloons, the pierce of the damaging radiation zone increases from 70 to 100, and pops Lead.

This upgrade costs $255 on Easy, $300 on Medium, $325 on Hard and $360 on Impoppable.

Appearance
This upgrade will give the Monkey Sub red paint near the front of the sub, underneath the gun, as shown in the artwork. Purchasing two of the Path 1 upgrades will give the sub a green cap and green-lensed binoculars. Purchasing two of the Path 2 upgrades will give the sub two guns, as well as yellow paint around the window on the side of the sub.

Summary
The Heat-Tipped Darts upgrade has a rather niche use, being quite ineffective for most purposes, but is still handy for certain scenarios whenever Leads or DDTs are a threat, or on Race Events when using Bloontonium Reactor. This upgrade is mostly relegated to custom challenges or very unique challenges in which this upgrade is needed.

Tips

 * The Heat-Tipped Darts upgrade can be somewhat useful when going towards Ballistic Missile, especially for Round 28 and 30. In particular, a 0-2-2 Sub can solo Leads when placed in a spot with decent range.
 * Extra damage to Lead Bloons via Bloontonium Reactor is hardly useful because the Leads will usually fully pop by the time they leave the radioactive ring. However, the extra pierce from this upgrade is useful for allowing Bloontonium Reactor to more reliably combat dense mid-game rounds.

Trivia

 * The Heat-Tipped Darts upgrade is actually named "Heat-tipped Darts" (with a lowercase "t") in-game.
 * "Heat tipped" is a descriptive phrase describing a metallic object is hot on its end.