Area Room Category Name Difficulty
Wrecked ShipPhantoon RoomAllDoppler rhythmIntermediate
The cooldown for missiles is 9 frames, but to avoid having an input not register by being too early, the ideal doppler spacing is 10 frames. This gives a tempo of 350 beats per minute, which this video essentially gives a metronome for.

This helps greatly with the Phantoon fight, although dopplers are also useful elsewhere in the game, like Spore Spawn, or missiling red doors.