Here is the full list of all 21 3x64 achievements.
The base game contains 20 achievements, and there is 1 DLC pack containing 1 achievements.
Use all types of powerups (standard and crafted) during single game
Achieve level 100
Reach 500 points without changing gravity
Destroy at least 5 iron blocks using TNT or Big TNT
Reach 1500 points
Destroy all irons at level 20 or higher (Simple Mode)
Destroy 7 blocks in one line (without using powerups)
Achieve combo 6 or higher
Clear the game board at level 10 or higher
Destroy the threat block just before activation
Destroy at least 15 blocks at once by gravity change
Place yourself in the top ten of the leaderboards
Send your first replay to the leaderboard
Use at least 9 powerups in one game
Finish arkanoid minigame without failure
Craft at least 4 powerups in one game
Destroy line during invisibility
Destroy 4 or more blocks in one row
Destroy a threat block using a powerup
Use your first crafted powerup
Reach rank 20 (Coming soon in Anniversary Update 1.3)