Troops are upgraded using Builder Elixir. Doing so may improve their hitpoints, damage, their special ability, or the number of the same type of troop that is able to fit into one Army Camp.
All troops (except the Night Witch) unlock their special abilities at Level Two, the abilities improving as they are updated. The Night Witch unlocks her ability at Level four.
Each time the Star Laboratory is upgraded (depending on what level) you can see Roman numerals (I-VI) in front that corresponds to the level of the Star Laboratory.
The star laboratory undergoes significant changes at on all of its levels.
At level 1, the Star Laboratory appears to be a building with a small telescope protruding through its top tied with ropes.
At level 2, the ladder is moved to the left side of the star laboratory with a ramp on the right.
At level 3, the telescope is longer and a ramp replacing the stairs on the left side. The door frames are also partially gold.
At level 4, the telescope is now golden along with the door frames and the ramp on the right side is replaced by a pressure gauge, similar to those on the Laboratory. The roman numerals also turn gold.
At level 5, the telescope becomes rotatable on top of the Star Laboratory using gears. The ramp on the left side turns into metal stairs.
At level 6, the telescopes aperture is larger and the type is changed with a refracted focal length, making the overall length shorter.
At level 7, a secondary, smaller telescope is added to the right of the primary.
Like the Clock Tower, it has Roman numerals corresponding to its level.
The Star Laboratory is the Master Builder's favorite building. This is mentioned in the tutorial.
Unlike most other Builder Base buildings, the Star Laboratory takes up a 4x4 space.
All troops can be upgraded to level two without having to upgrade the Star Laboratory to match the Builder Hall level.
The Star Laboratory has the same research icon (with a sword and a spell bottle) as the Laboratory. However, the Builder Base has no spells.
Tapping this icon displays information about the Star Laboratory, such as Level and Hitpoints.
Tapping this icon begins upgrading the Star Laboratory to the next level, if you have enough resources and a free Master Builder. When the Star Laboratory is at maximum level, this icon is not shown.
Tapping this icon instantly upgrades the Star Laboratory to the next level, at the cost of one Hammer of Building if you have one. When the Star Laboratory is at maximum level, 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.