There is a wonderful competition out there called js13kGames. The name explains its objective very clearly. You have to create a game that weighs 13kb in JS. The game has to fit the theme that the author of the competition appointed.
This year's the theme is: Offline
I tagged this post #beginners for a reason. It is a great opportunity to learn how to design and make a game. Their website has a wonderful "Resources" page that links to many tiny libraries and frameworks that you can use to create your game.
To encourage people to participate in a competition, there are many valuable prizes, like a year of GitHub subscription, CodePen Pro plans, and more!
You don't have to rush! Competition ends at September 13th, so you have enough time to think, create and test your game.