The CSS  rotateX()  function rotates an element around the x-axis in a three-dimensional space. Specifically, it vertically flips the element, making it tilt backward or forward, depending on the angle set. It is one of many transform functions used in the  transform  property. The x-axis is the axis of rotation, so the element turns vertically. Imagine a pin is stuck to the left side of an element and it can only turn up or down. In the demo below,  rotateX(0)  is given as the element’s default rotation: .demo-element { transform: rotateY(var(--deg)); transition: transform 0.3s ease; } The  rotateX()  function is defined in the  CSS Transforms Module Level 2  specification.…