Dr. Robotnik will fire an icy blast in one of three directions: either left or right out of the weapon extended from the bottom, or down from the bottom of the mobile itself. For a short while after the fight begins, these blasts will occur in a regular pattern of left-center-right-center etc, but after that it becomes random. A particularly frustrating trick of Robotnik's here is firing downwards twice in succession, catching the player out.
Six hits causes the main weapon of the mobile to break up. Two more hits are required to defeat it, preferably from in front. The only real threat to the player at this point is the icy gas leaking out of the back of the damaged mobile which still has the same effect as before.
This is one of the toughest bosses in the game mainly due to the random nature of the attacks. When playing as Knuckles in Sonic the Hedgehog 3 & Knuckles, the EggRobo will retract the platform just after firing icy gas to the sides, making the already difficult jumps very hard to execute. Super Sonic can easily destroy the machine thanks to his increased jump height (and indeed his invincibility) but when playing as Tails has no Super State is normally available here, meaning the boss must be defeated in a more conventional way.