You've learned how to write CSS. Now learn how NOT to write CSS, along with other secrets of modern web development, except for vertical centering which is impossible.
This book is the counterpart to the open-source Cavepaint CSS framework: https://cavepaint.github.io/cavepaintcss/
Want to support Cavepaint? Buy the book. Also, the book is good too. It's about the zen of setting up web development projects with multiple teams. It's about how and where to put your ideas on how stuff should look. And also about CSS. And also not-CSS.
PAY-WHAT-YOU-WANT PRICING GUIDE
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3.00: "I hear SF has great homeless services."
5.00: "I felt like a soundboard for your rants."
10.00: "It was good but come on."
20.00: "It's slightly less valuable to me than a Blu-ray."
22.00: "The Blu-ray line worked on me so I bumped it up a little."