"The iconic ground defense, built to last! This classic makes the Master Builder a bit sentimental."
Level 1
Level 2
Level 3
Level 4
Level 5
Level 6
Summary
Cannons are a defensive building in the Builder Base. They are unlocked at Builder Hall level 2 (they are fixed from their ruin), and are the first defensive building in the Builder Base.
Cannons are both cheap and quick to upgrade at lower levels.
Make sure Cannons are placed within range of Firecrackers or Air Bombs, because Cannons are unable to target air units.
Upgrade these structures first at lower levels, as they are one of your main ground defenses. They are also the cheapest and one of the most common defensive structure available, which makes them a good initial investment.
Offensive Strategy
Cannons are one of the few defensive structures that cannot attack air units. This makes them easy pickings for Beta Minions or Baby Dragons if they are not within range of Firecrackers, Archer Towers, Hidden Teslas, or Air Bombs.
The Beta Minions' Long Shot ability allow them to destroy a cannon while out of range if there are enough and placed correctly.
Cannons are only able to damage one unit at a time. This makes it very easy to overwhelm them with large groups of Sneaky Archers or Raged Barbarians.
You can destroy a lone cannon without any distraction buildings with three Sneaky Archers of relative level.
Upgrade Differences
Cannons undergo significant changes at levels 2, 3, and 4.
At level 1, the Cannon consists of a short dark metal barrel mounted on a crude, four-legged wooden platform.
At level 2, the Cannon's base receives a wooden stabilizer tied to the legs with ropes.
At level 3, the Cannon's leg stabilizer becomes stouter and the cannon becomes larger. The base itself rotates 45 degrees within the 3x3 square (ostensibly to accommodate the later, larger upgrades of the Cannon).
At level 4, the Cannon barrel receives two decorative latitudinal ridges, one midway along the barrel and one at the rear. The platform's leg stabilizer is removed in favor of a larger and stouter main support platform with much shorter legs.
At level 5, the Cannon base's wooden legs are replaced with metal ones and its metal ring which it pivots on gets wider.
At level 6, pieces of metal bolted by a metal bolt are added to the side of the cannon.
The appearances of the cannonball changes with level, along with its size.
When first constructed, the cannon shoots small, light grey color balls.
At level 2, it shoots bigger balls.
At level 4, the balls becomes even bigger and becomes darker.
Trivia
The Cannon is automatically repaired when the player upgrades to Builder Hall level 2, even though the Master Builder does not appear to repair it.
When viewing your village, the Cannons will appear to aim randomly about. However, they will mostly be aiming away from the Builder Hall. If the Cannons (or the Builder Hall) are moved, the Cannons will instantly orient themselves to point away from the Builder Hall's new relative location. This remains true even when the Cannons are being upgraded, though it will not move.
The Cannon is able to rotate in a full 360 degrees.
The Cannon's barrel expands slightly whenever it shoots.
On 5/26/2017, Builder Hall level 3 received an extra cannon that was previously unlocked at Builder Hall level 4.
On 6/26/2017, the Cannon received level 6, due to the release of Builder Hall level 6.
Icon Descriptions
Tapping this icon displays information about the Cannon, such as Level, Damage Per Second, Hitpoints, Range, Damage Type and Targets.
Tapping this icon begins upgrading the Cannon to the next level, if you have enough resources and a free Master Builder or O.T.T.O. When the Cannon is at maximum level, this icon is not shown.
Tapping this icon instantly upgrades the Cannon to the next level, at the cost of one Hammer of Building if you have one. When the Cannon is at maximum level, or the Builder Hall requirements for the next level are not met, this icon is not shown.
Tapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of the displayed number of Gems.
Tapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of one Book of Building. This icon is only shown if you have at least one Book of Building.
Tapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of one Book of Everything. This icon is only shown if you have at least one Book of Everything but do not have a Book of Building.
Tapping this icon, which is displayed only while an upgrade is in progress, cancels the current upgrade and refunds half of the upgrade cost.