Simple CSS / HTML

Easy project. I give you an image in Black and White. You create a CSS similar to this one (as in the effect on click or on tap) [login to view URL] The image should invert its colors through CSS. I will send you the inverted image anyway. The image should stay "changed" if the user tapped it once. If the user taps it again, the image returns to its normal state. This should work in mobile phones, and computers (events on tap / on click). Deliver: HTML and CSS (with anything else you consider you need). Please comment your code. Feel free to ask me any question.