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