&gt; They really are a marvellous thing; my favourite example would be the construction of truly responsive interfaces, tweaked for optimality at many levels and continuous, rather than just things with three or four breakpoints; with preprocessors, it’s tedious and painful;<p>Anything with preprocessors is tedious and painful, yet I&#x27;ve been hand-writing fluidly responsive layouts for years without predefined &#x27;breakpoint&#x27; jumps in the design. What is it about CSS variables that allowed you to change your style?