Playing as SonicEdit
Sonic arrives at a flat portion of ground with a few pieces of scenery. Dr. Robotnik will descend from above with the Drill Mobile, stop in mid air, pivot the drill so it is pointing downwards and then slam into the ground. This destroys the land causing Sonic to fall, after which, Tails arrives (whether or not the player is playing with Tails following Sonic), carrying him through the air. The Drill Mobile will charge across the screen from three different angles; either from above, below or from the left, in this order: Left, left, down, up. The player can move around the screen using any direction on the D-pad.
Playing as TailsEdit
The same sequence of events happens as with Sonic, but this time Tails does not have anyone to carry and must attack the Drill Mobile himself using his spinning tails.
Playing as Knuckles (Sonic 3 & Knuckles only)Edit
The EggRobo version of this boss is very much different to when playing with Sonic or Tails. Instead, the battle is fought in a tunnel. The Drill Mobile will fire a spiky chain from one of four different locations (either from the ceiling or the floor) which then re-emerges from another location. The Drill Mobile itself will then travel along this chain before repeating the process.
Defeating the Drill MobileEdit
When playing as Sonic or Tails, Robotnik can be hit a few times in the opening scene where he destroys the land the player is standing on. When playing as Super Sonic, Robotnik can actually be hit more than the eight times that is normally required to defeat a main boss. If this is done, Robotnik's mobile will be destroyed after just one hit in the main flying sequence. In any case, Sonic must jump from Tails' arms to attack Robotnik, taking care to avoid the drill and the flames from the engines.
As mentioned above, Tails must use his spinning tails to attack Robotnik from below. This is best done when Robotnik is traveling from left to right.
Knuckles attacks the boss in a similar way to Sonic, with eight hits being required to destroy it.