Gravity Φ

Gravity Φ is an Extreme track that takes place in Outer Space.

To unlock this track, you must beat all other Outer Space tracks on hard difficulty (Gold Medals), and type "stardriver" (without the quotes) at the track selection screen.

Description
The track has a large Φ symbol in the middle. The Bloons take the top entrance, take a right turn at the interection, go around the curved path, and when they reach the intersection again, they take another right, then proceed to the exit at the bottom. The surrounding area is completely Outer Space.

Trivia

 * This is the Reference.