Here is my 100% Achievement guide for Hardcube!
This is for jumping off a level 15 times in one level.
This can be easily done from the tutorial but i waited for Level 1-1.
Simply press A as soon as you start to jump off.
Do this 15 times and the achievement is yours!!
Go to 3:10 in my video to see where i get this.
Hope This Helps!