What is that yellow circle around my ACU ? / How can I disable the Range Ring ?
From FA Forever Wiki
What is that yellow circle around my ACU ?
They are called range rings and indicate the distance each "builder" (ACU, SCU, engineers) can construct a structure before having to move.
Range rings were in supcom vanilla (Supcom 1), and they are the maximum build range of that unit.
Be aware that a building can be built mostly outside that ring as long as a small part of it is inside the range ring.
How can I disable the Range Ring ?
Pressing Ctrl + Alt + Num 0 will toggle the range rings.