Here is the full list of all 26 BIT.TRIP BEAT achievements.
Got a PERFECT in GLaDOS' level
Achieved a multiplier of 50 in Normal difficulty
Chained 500 Beats
Beat the game in one sitting without getting a Game Over
Get a PERFECT in 1-1 using only a game pad
Experience the joy of a serene suburban afternoon
Beat the game on Normal
Beat Growth in Normal difficulty
Block all Beats in all Challenges
Watched the hidden cutscene
Chained 200 Beats
Beat Descent in Normal difficulty
Block 10,000 Beats
long fall
Make a bell chime in Descent
Got a PERFECT in sunny 1-1
Chained 100 Beats
Block all Beats during a Challenge
Register a high score on the leaderboards
Beat Transition in Normal difficulty
Miss a Beat with an extended Paddle
Escaped Nether Mode
Got a PERFECT score in Transition
Got a PERFECT score in Descent
Got a PERFECT score in Growth
Achieved a multiplier of 100 in Normal difficulty