Sentry Gun

Sentry Gun is the first upgrade of path 1 for the Monkey Engineer that allows it to create sentry guns within its range. The sentry guns shoot nails, and each nail can pop 2 bloons. It is very useful for the early rounds as it acts like several dart monkeys all attacking at once. The Monkey Engineer can create up to 3 Sentry Guns with no fire rate upgrades when he is upgraded to this.



Costs

 * Easy: $385
 * Medium: $450
 * Hard: $485

Trivia

 * The player can select a sentry gun, and it will show the player a pop count. The player can also sell the sentry for $0. The sentry automatically gets unselected when it collapses and disappears.
 * The Sentry Gun is most likely a reference to Team Fortress 2, as well as the Soap Dispenser and maybe even the tower itself.