Here is the full list of all 18 Elastrix achievements.
Beat level 24 of the Gravity chapter without collecting any gems.
Finish the Gravity chapter.
Get Perfect Shots in all levels of the Gravity chapter.
Hit a high score of 5000 or more in Trixball.
Hit a high score of 3000 or more in Trixball.
Get over 1000 points in Trixball in a single shot.
Hit a high score of 1000 or more in Trixball.
Do a Trixball shot that only scores 10 points.
Shoot 200 Trix out of the cannon.
Beat level 7 of the Gravity chapter without collecting any gems.
Beat level 23 of the Classic chapter without collecting any gems.
Beat level 8 of the Classic chapter without collecting any gems.
Have at least 10 Trix on the screen at the same time.
Keep a single Trix alive in a level for more than 60 seconds.
Solve a level without using any kind of band.
Get Perfect Shots in all levels of the first chapter.
Finish the first chapter.
Get Perfect Shots in any 5 levels of the game.