The Star Laboratory allows the player to upgrade their troops, much like the Laboratory in the Home Village.
Like in the Laboratory, if the Star Laboratory is upgraded while research is in progress, the research will continue as if the Star Laboratory was not upgraded at all, but with one exception: if an upgrade within the Star Laboratory would complete while the Star Laboratory itself is being upgraded, the upgrade will not complete until the Star Laboratory finishes upgrading.
Troops are upgraded using Builder Elixir. Upgrades 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 unlock their special abilities at level two, except the Night Witch, whose ability is unlocked at level four. The abilities improve as a troop is upgraded.
Each time the Star Laboratory is upgraded (depending on what level) you can see Roman numerals (I-IX) in front that corresponds to the level of the Star Laboratory.
The Star Laboratory undergoes significant changes at levels 1, 3, 4, 5, 6, and 9.
At level 1, the Star Laboratory appears to be an observatory-like 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. The rope is removed from the telescope, and its rim becomes stone.
At level 3, the telescope is longer and a ramp replacing the stairs on the left side. The door frames are also partially gold, and the telescope's rim becomes metal.
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. The blue gear on the top by the telescope turns golden.
At level 6, the telescope's 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.
At level 8, a tertiary telescope is added next to the secondary on top of the primary. The pressure gauge also turns golden on top.
At level 9, the main telescope is reversed to normal length. The needle on the gauge also disappears. A stone also is placed behind the gear.
Like the Clock Tower, it has Roman numerals corresponding to its level.
The Star Laboratory is the Master Builder's favorite building, as 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 2 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. Ironically, the Builder Base has no spells to upgrade.
The upgrade time and cost of each troop "smoothly" follows the time and cost to unlock it (i.e. upgrading the Builder Barracks to the corresponding level).
Interestingly, in the Builder Base's Star Laboratory, when clicking a maxed out troop for your Star Laboratory level, the game shows you all of the levels and upgrade bonuses, as would normally happen if the troops was not maxed. However, in the Home Village's Laboratory, if you have maxed out a troop or spell for your Laboratory level, and click on it, the game tells you, "Level __ Laboratory required".
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, 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.