From Sonic Retro
There are several benches in the room which have light switches on them. As the Egg Phantom flies around the room, players must jump on the switches to lure the boss to the light. If the Egg Phantom touches a light, it will become transparent, revealing Eggman Nega's hovercraft. This is the player's chance to attack. The phantom's only offensive attack is touching the player while Eggman Nega is concealed.
Six hits from one player marks the end of the fight and victory for the player.