To check how much battery your doppel has, using the straps as a guide, tap back and forth across doppel three times and then count the buzzes you feel.
Four beats = 75% - 100%
Three beats = 50% -75%
Two beats = 25% - 50%
One beat = 0% - 25%
Tip: Touch controls work best when doppel is on your wrist or when holding it in your hand as opposed to laying it flat on a surface. You may also find it easier to practice with using your thumb as you get used to how they work.