Inside the container is a green LED that's part of the "liquid analyzer." See, what you put inside determines the sound of your distortion. How easily it conducts your guitars AC signal determines the amount of gain and the opacity of the liquid determines the amount of treble and bass. So, depending on what you put in there, you could get a full throated roar or a narrow telephone like distortion.
Otherwise there's not really any controls to be found on the Minibar. There's an on off switch and a volume knob and... that's it. All your other typical distortion controls are determined entirely by your choice of liquid. Want to know what your favorite whiskey sounds like? Or perhaps you're partial to a nice root beer. Or, maybe, you want to get as metal as possible and buy some pigs blood from your local butcher.
The Rainger FX Minibar is available now for £99.17 or around $129.