I write CSS + HTML. I use LESS, SASS, and vanilla CSS, depending on project. This is, professionally, nearly all I've done since 1997.
Why would you need someone who specializes in this, you may be asking? Your devs handle the front end, it's all fine.
I can tell you in 21 years in the industry what I've experienced:
Everywhere I'm hired to take the burdon of visual frameworks off the development team, the devs are relieved.
Design is happier, as they have a go-between who understands both worlds.
Production time ramps up as devs get to do what they're excellent at; building the engine, knowing the visual part is taken care of.
Companies can stop guessing if their product will work in certain browsers, or in certain mobile devices.
I've written CSS + HTML frameworks from the ground up for award-winning apps & websites written in PHP, ASP and Angular. I've made a React Point of Sale system white-label-able, designed and coded a digital menu for in-store 55" 4K TVs, and repaired more WordPress sites than I can name. I can help your company, your project, your dev team. Because this is what I love to do, I work hard to do it well.
One of the apps I wrote my largest framework for, while at Ayogo, has been released into the wild and I am unimaginably proud; AllyQuest. You can read up on the study taking place around it here: A Gamified Smartphone App to Support Engagement in Care and Medication Adherence for HIV-Positive Young Men
As well as Ayogo's official pilot study here: AllyQuest Pilot Study Results: App Usage Positively Correlated With Self-management Outcomes
Visit my Codepens