The Yellow Desert boss is a mech consisting of a capsule similar to that of the Egg Mobile (albeit in a vertical position instead of the usual horizontal one). It has a protective glass cover, yellow edges, two headlights and a red bust, as well as mechanical arms and legs connected to the capsule by red joints, the former sporting four-fingered hands. It also has large feet with giant red armor on top of them. It wields a red spear linked to the main control capsule by a cable and is decorated with a red ribbon. Color-wise, the mech is mostly dark gray with the edges of its protective glass cover being yellow while the bust, spear, ribbon, joints, and feet armor are red. Egg Mobile-styled yellow and black hazard stripes can be seen on the sides.
Powers and abilities
Robotnik's mech has the power to materialize a cloud that is solid enough to support the mech itself. This cloud can also be ridden by the mech as its means of transportation. It also wields a spear that it can use to attack foes quickly.
In Sonic Blast, Dr. Robotnik used this mech to attack Sonic and Knuckles when the duo was passing through Yellow Desert Zone. In spite of Robotnik's efforts though, his vehicle got destroyed by the two heroes in the end.
When the player arrives in a wide empty area in the caves of Yellow Desert Zone Act 3, the screen will start pushing the player into the actual, still empty, battle arena. Dr. Robotnik will then arrive from the right corner of the screen and wait a few seconds before moving off-screen slowly. He will then swiftly move all the way to the left side of the screen while using his spear to pick the ground in a diagonal way (at the bottom-left of his position) until he goes off-screen again. Robotnik will then reappear from the left side of the arena, restarting the whole process over again (albeit from the opposite position each time) until he is defeated.
This boss needs to be hit twelve times. However, these hits must be dealt precisely into the protective glass cover of the Yellow Desert Zone boss. Trying to hit this boss vehicle from any other spot will simply bounce the player back without dealing any damage. Hitting this boss below the protective glass cover while Robotnik is picking the ground is particularly bad since this will bounce the player right into the spear. Hitting Robotnik when he does not move at all will cause him to go off-screen prematurely to execute his staff attack afterward.
After being defeated, the Yellow Desert Zone boss will blow up before disappearing in a flash of white, clearing the Act.