Here is the full list of all 23 GAUGE achievements.
Unlock 15 life extensions.
35.000.000.000
28.000.000.000
Get 50 lives.
Score 1.000.000.000 points in touch mode.
Score 600.000.000 points in time mode.
20.000.000.000
Get 100 bonuses in one game.
Error#14.000.000.000#!$)^(=_001'*!
----- 10.000.000.000 -----
Cheat code activated.
Meow 6.000.000.000 Meow meow meow.
Play 90 seconds with 2 gauges.
Press the spacebar 5000 times in one game.
Play 1200 seconds straight.
Score 2.000.000.000 points in limitless mode.
Score 1.500.000.000 points in time mode.
Score 2.500.000.000 points in touch mode.
Score 1.000.000.000 points in hard mode.
Score 2.000.000.000 points in hard mode.
Score 10.000.000.000 points without using second gauge.
Score 20.000.000.000 points without using second gauge.
This achievement is here to prevent you from filling achievement gauge to 100%... and die. You can't unlock it.