CSS Diner
A very nice game that lets you learn CSS, very fast. Simply just complete all 32 challenges and make sure you understand the intuition.
Grid Garden
A web-based game that you have to fill in some CSS properties or values related to CSS Grid to either water the carrots, or to kill the weed plants.
Flexbox Froggy
A game for learning CSS flexbox. A fun way to learn how to format web content.
CSS Challenges
CSS Challenges is a resource that offers fun and playful ways to practice your CSS skills. You can do that by playing CSS challenges/riddles or by taking quizzes.
Flexbox Zombies
Each section of this game unravels part of the plot, gives you expertise over a new flexbox concept, and presents zombie survival challenges that force you to solidify your new skills as your life depends on it.
https://mastery.games/flexboxzombies/
Credit goes to :@SajalShlan