In its core, putting together a WordPress theme is a rather simple task. WordPress delivers a really friendly environment and makes it clear which PHP functions to use for what purpose along the way. However. Even though it’s simple, it’s far from easy, and especially if you want your theme to be mobile-optimized. There’s a range of unique issues that you ought to overcome if you want to end up with a quality product that loads fast, operates in a predictable way, and (what’s the most important thing) is user-friendly and accessible to people using different devices and screen sizes.