Orbit 2.0, part 3: heavy enemies head home. Fortress, Mirror, Plague, Lance and Spinner now remember where they spawned. After 30 seconds of chasing you — or immediately if you leave their ring toward the outside — they give up and fly back there without shooting. Once out of sight, they’re gone. Back home they rest for 20 seconds; get within 450 px of them in their ring after that, and they wake up again.
That keeps the interior dangerous without having it follow you all the way to the outer ring. Measured: a fortress chases for 30 s, heads home, rests for 20 s; a lance breaks off as the ship leaves the inner ring after 2.1 s, and is gone afterward.