These are assignments from the well-respected Full Stack Web Developer training curriculum called "The Odin Project". Learning through TOP is self-paced, and the content is thorough in its coverage. It is an Open Source project maintained by a passionate group of volunteers who maintain a standard of excellence.
I began at the "Intermediate HTML/CSS" course, which is the beginning of their Full Stack Javascript Developer curriculum. It helped me to refresh my skills on everything from semantic HTML to recent improvements in CSS layouts like CSS Grids and Flexbox.
The next (hefty) section of the curriculum covered a lot of important Javascript concepts and computer science basics like advanced data structures. I was already familiar with most of this content, but it was a good chance to refresh my memory on certain things I hadn't used in a while.
Then the curriculum moves on to "Advanced HTML/CSS", which covered animations, transitions, web accessibility standards, and responsive design.
There's a reason React is as popular as it is in the tech world, and The Odin Project has given me a chance to improve my React skills and understanding beyond the dozens of hours of video tutorials I've completed in the past.