The player controls Sonic the Hedgehog during the boss battle. To defeat Chaos, all the player has to do is jump onto its brain to deal out damage. The player must dodge Chaos' attacks, while it is mainly extending its arms in an attempt to hit the player. After each hit, Chaos will turn into a puddle and move to a different location in the battlefield.
After one hit to the brain, it spins around its axis while attacking with energy-charged fists. After two hits to the brain, Chaos will jump onto street lights surrounding the player and attempt to hit the player by extending its arms. After dodging these hits, it will eventually jump back to the surface, leaving him vulnerable for an attack. Once the player hits Chaos for the third time, it is defeated and the battle has been won. If the player fails to attack when Chaos returns to the ground, it will use the same attack when it has been hit two times.
|Boss: CHAOS ver.0, 2, 4||Jun Senoue||2:27|
- Sonic is the only one who fights Chaos 0 in Sonic Adventure.
- Despite appearing before Emerald Coast, this boss cannot be fought in the demo version on the Xbox 360.
- If the player fight this boss again after gaining the Ancient Light, it is possible to use the Light Speed Attack on Chaos while it is on the pole and finish it there. This can trigger a rare animation of Chaos where it will fall from the pole until it puddles on the ground.