The up and down arrows on the front of the brush control the intensity of the vibrations, going from level 1 (gentlest) to level 10 (strongest).
The Intensity Wave on the back of the handle lights up in correspondence with the intensity level!
If you are on on intensity level 1, for example, only the bottom tip of the intensity wave will be lit.
If you are on intensity level 10, the whole wave will be lit.
The 4 modes, on the other hand, combine different patterns of speeds and rotations so you can customize your clean.
Pick the mode you want by pressing the power button consecutively within 5 seconds of turning it on.
Every time you press it will switch the modes: Squeaky Clean -> Sparkle -> Sensitive -> Self-Care.
The icon for the mode you choose will light up.