Phase is a interactive music game developed by the creators of the Guitar Hero series, with similar gameplay. The gameplay is dynamic, as levels are built based on the content of the user's iPod. For every song, the game creates a new, custom challenge, similar to the earlier iPod game musika. The screen shows a 3D road consisting of 3 white lines, disappearing into the distance, and three circles near the bottom of the screen. As the notes (discs and dots) appear from the top of the lines, players need to match them in the circles by tapping the clickwheel (left - center - right), or gliding the it to catch flowing sweeps. Various backdrops are rendered along the road with different characters and environments.
Unlike the Guitar Hero games, the music does not stop when a mistake is made. Every song is divided into different checkpoints and the player's performance is ranked by stars. If too many notes are missed, the game ends prematurely and the player loses a life. Long streaks result into combos and the game also shows the overall accuracy and total score.
There are 2 gameplay modes: QuickSpin (a single song at a time) and Marathon (a session of 5 songs with an increasing difficulty).