This is the only time you will encounter Rubble (as of July 2017), which is a pity, as it is a boss quite different from the other bosses. Rubble is a huge tank and the only land based boss vehicle you will meet. Also Rubble will launch smaller tanks to attack you.
A tough struggle and great fun!
Video: Heroic Solo
Buzzsaw A, Hazard S, Beetle S
1 minute 9 seconds
Video: Heroic Solo
Eagle A, Legatus S, Cougar A
1 minute 3 seconds
Gameplay
The different phases when you battle Rubble are not as clearly defined, as with other bosses.
Phase 1: Five guns will fire at you from front of Rubble. They will spew 6 rapid shots each in rapid succession. Take them out, preferably one by one.
Phase 2a: Two different sets of two turrets will take over, firing larger and meaner shots at you. Again, try to focus on one target at the time. If you are not quick enough in taking out these turrets, they will be left for the next phase.
Phase 2b: Things happen fast now. The main turret of the giant tank will now, almost reluctantly turn counter clockwise towards, and fire a massive barrage of missiles. Then the main gun with a barrel the size of your ship will be turned against you, firing chain linked huge glowing bullets at you. The missile barrage will strike again, but at least with less force.
You just have to survive and kill everything that appears and try to survive this bullet hell.
Phase 3: Now a single, large red bar will appear, which is the armor left for the entire tank. The entire main turret of the tank will rotate, spewing circles of bullets around. It will only stop to release a couple of minor tanks taking shots at you.
Killing Rubble lets you do a satisfying flyby over the wreckage. Nice touch!
Advice
Eagle, once you’ve got it, is always good fun to bring to a boss battle. But even Eagle seems to struggle with some of the Rubble’s turrets.
Buzzsaw though, is our favorite to battle Rubble. Otherwise, take one of the usual boss killing planes.
Select plane overdrives and brobot specials that work from a distance. The bullets coming from Rubble, will spread somewhat, and will therefore be more easy to dodge at a distance.
Menace is the reload speed enhancing brobot which you will get early in the game. Menace’s special do some damage to bosses as well. Definitely bring Menace, unless you have an other speed brobot to test.
Nayad (stronger beam, but shorter duration) and Doom (weaker beam, but lasts much longer), are good brobot options for your second brobot. Scarab, though difficult to time, seems to do heavy damage to Rubble as well.