Placing a pole cost 5

Contols :

Right Clics  (On nothing)  :   Place "Minus"      (you need to have selected a "Plus")

Left Clics     (On nothing)  :   Place "Plus"          (you need to have selected a "Minus")

Clics  (On a pole)                   :   Link this pole to the selected pole (if they are opposite) to a maximum of 3 per poles.

Confuse ? :

the goal is to protect the core as long as you can. Enemies will try to attack it and break linked in there path. The core die if all links are broken. 

When a "plus" and a "minus" pole are linked they produce power.  You need power to place them but the more power you got, the more enemies appear... If you have trouble placing pole it's probably by due to a lack of power (it cost 5).

Credits :

audio from https://freesound.org