Enroll as a [Defender] and take up the mission to protect your solar system from the threat of an imminent Bluul invasion!

[Controls]

[R] to restart level
[P] to pause/unpause
[H] to hide the User Interface
[Escape] return to Menu
[N] to start the wave
[Right Click] to sell turrets/walls
[Space] toggle auto-fire on/off
[Double Click] on a turret to open upgrade panel
[Shift+Click] a TURRET to automatically purchase it’s upgrades

[Additional Tips]

1.The border of the screen is not considered solid, so don't rely on it when building!
2.The [Pillar] price is increased by 50 with each purchase.
3.Don't forget to hold [Shift] pressed when building in order to build more than 1 object.
4.Upgrades should be prioritized over new turrets since they're more effective!
5.Long corridors can be more useful than 1-2 offensive turrets.
6.Press [H] to hide UI if it's blocking you from accessing a turret.
7.Use [Shift + Click] to automatically upgrade turrets without opening the Upgrade Panel.

Good luck and have fun!

[Credits]

Factory Ambience by 'yd' from opengameart
Atmospheric/Menu music by 'qubodup' from opengameart

Special thanks to "Maggrig" for testing and reporting lots of bugs!