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