Complete three weekly challenges in the "Catastrophic" Mission and you will be rewarded with a special loading screen. On this very radioactive one, the green paint tends to run leaving a fluorescent mark on the wall that gives the coordinates of the Secret Hidden Battle Star.
You can read the inscription "E78 F78" meaning that you must go to the intersection of cells E7, E8, F7 and F8 to find the star.
See you next week for another Secret Hidden Battle Star!
