Sentry Gun is the first upgrade of path 1 for the Monkey Engineer in Bloons TD 5 Deluxe, Bloons TD 5 Mobile, Bloons Monkey City and Bloons TD Battles Mobile. It allows the engineer to create temporary sentry guns within its range. The Sentry Guns shoot nails which can pop 2 bloons each. One Sentry is deployed every 10 seconds and lasts for 25 seconds. Up to 3 sentries can be active at any given time, without additional upgrades or attack speed buffs to the engineer himself.
This is a very useful upgrade for the early rounds as it acts like several Dart Monkeys all attacking at once.
Tips[]
Deployed Sentry Guns can be selected to change their target priority or sell for $0 to give space for another tower to be placed. Sentries do not occupy footprint space for other towers in Bloons TD Battles Mobile.
In the case of BTD5 Deluxe, Bloons Monkey City Flash and BTD6, Sentries' target priority is determined by the Engineer who has spawned them. In BTD5/Battles/Monkey City Mobile, however, Sentries default to First no matter what target priority the Engineer has.
They are effective on daily challenges and special missions where the amount of towers is limited, as they do not affect the total tower count.
Sentry Gun upgrade icon in BMC Flash, with several discounts
Sentry Gun in BTD5
BMC Flash
Flash sentry in-game
BMC upgrade portrait
BMC Flash upgrade icon
Unlocking Sentry Gun in BTD5 Mobile
Trivia[]
If the Engineer is upgraded to Sprockets, any new sentries spawned will have the name "SentrySprockets" on non-mobile versions. These sentries are not affected by Monkey Knowledge in BMC Flash.
The Sentries actually might be based off of the Sentry Turret from Valve's Team Fortress 2.
The BMC Mobile sentry is missing the "OnlyTargetPlacementLocations": true line of code it has in BTD5 and Battles, causing the sentries to spawn anywhere, including on the track, water and unplaceable spots.
When a sentry runs out of time, it explodes. The explosion is visually the same as the Splodey Darts one from BTD5.
If the engineer is sold in the BTD5 Mobile generation games, all of their sentries disappear instantly.