One of the things I have always done to cement my knowledge in a programming language or environment is to write small applications using that language or in the particular environment. I have recently had to take up web development and thanks to Brad Traversy's courses on Udemy it has been a relatively painless experience. Okay, somewhat painless. There is still a world of difference in programming a web application that has to work across the multitude of screen sizes that are available today.
I'm working in Vanilla HTML/CSS/Javascript because I want to be well-versed in those items, Javascript especially because everyone seems to learn a framework with no understanding of what goes on underneath and that has always been something of a cocktail for disaster in my experience (yours may vary, of course).
In any case, Tunnels & Trolls by Flying Buffalo is one of the oldest fantasy role-playing games. In looking for a first small project, a simple character generator seemed to be about the right size, i.e., one that could be finished in a few hours. I make no claims to being a great web designer, but the functionality is there and as I dig deeper into the technologies I will likely continue to enhance it.
If you'd like to have a look, you can see it here.