Aaaaah, the checkbox hack. What a thing my friends! Hugo Giraudel is sure you’ve all heard about the checkbox hack before. It’s probably the most common way to handle a click event in CSS. It relies on, well, a checkbox. What’s cool about a checkbox is the fact that it’s binary. It’s either checked or not checked. There is no “half-way” checked. This is why the checkbox hack is a pretty reliable way to trigger a click event in CSS. Let’s make an example. As you can see, it relies on the :checked pseudo-class and on the general sibling selector ~. Please note that it also works like a charm with the adjacent sibling selector +. Basically, it says “if the checkbox is checked, then the following elements with the .to-be-changed class will be red”.