Electric portals

The  is a hazard in Bullethead. It is a Portal that spawns Black Flying Bugs.

Attack
The Electric Portal will suddenly appear on the screen. It will start small, but get bigger, and bigger. When it gets to its usual size (as shown in the image), it will spawn 5 Black Flying Bugs.

If it isn't destroyed soon, it will spawn another 5 Black Flying Bugs. It can take some time to destroy the Portal.