Review (1/5): I have an older version from the same company ( 2 buttons) that was a lot better.
The older version ( 2 buttons) it had a red/green/off light to define off constantly on or intermittent. The light button would cycle through the lights to select any of them and / or rotate through them. very simple and it worked good. this one has a sleep button that doesn't seem to do anything and its either constantly on or off. No light to let you know.
One other thing the old one turned the light off when it was empty, and this one stays on even when empty. buy the old one if you can. This one cost $3 more and it sucks....