Hidden Palace Zone boss

Brass Eggman is an optional boss in the 2013 mobile re-release of Sonic the Hedgehog 2, replacing Drill Eggman II should the player branch into Hidden Palace Zone rather than finish Mystic Cave Zone Act 2. The player has to do eight hits into Eggmobile to defeat this Dr. Robotnik.

Battle
Dr. Robotnik flies in front of a giant archaic organ. He will hover just out of normal jump height. The massive trombone horn on his Eggmobile will activate every few seconds. He begins with four descending notes, causing four hazardous spiked balls to fall from the ceiling and land on the water below the arena. The water will then rise over the platform, taking the floating balls with them for a second or two. After being lowered to the original water level, the balls will detonate and emit a vertical splash that must be avoided. After a few more seconds, a long and loud bellow will emit from Robotnik's horn, causing the screen to shake until one larger spike ball descends. This variant homes on the player's character until it also explodes, thrusting a large jet stream into the air. After this, Dr. Robotnik will encore indefinitely.

Per usual, eight hits will mute the machine. During the first phase of attack, the player can take advantage of the bouyancy of the water to reach the Eggmobile, although the small flames at the bottom of the Eggmobile are damaging unlike other bosses from this game. The main method of attack comes in the second phase, where the player can you lure the Eggmobile above the large homing bomb as it erupts. If hit, the Eggmobile will be rendered stunned on the ground, giving the player enough time to land multiple hits. Super Sonic and Tails can reach the boss easily, negating the need for waiting.

Trivia

 * This appears to be an entirely new boss design by Christian Whitehead, as no concepts for a boss machine were finalized or perhaps even intended for Hidden Palace.
 * The construct in the background appears to be based on the famous organ of Alexandra Palace.
 * There is a glitch with inflicting the final hit while the Eggmobile shakes just after being paralyzed, causing the damage counter to roll over and become indestructible much like the Final Zone.