Learning CSS isn’t the easiest. But the community helped solving that by creating a lot of interactive games online (as the best way to learn is with games).

Selectors

If you want to learn CSS selectors, you can try out CSS Diner 🍱:

Flexbox

For flexbox, you can try out Flexbox Froggy 🐸

Grid

And finally, you can learn CSS Grid with Grid Garden 🧑‍🌾