Whether you want to understand the fundamentals of coding, dig into Einstein’s theory of relativity, or brush up on high school calculus, Brilliant offers interactive courses to help get you there.

What we love: The app’s free introductory lessons provide a perfect primer on deep STEM topics, like artificial intelligence through neural networks, computer science, and everyday physics. Advanced courses cover multivariable calculus and even quantum computing.

Quick tip: Let competition fuel your learning with the Leagues feature. After earning your first 175 experience points (known as XP) you’ll be entered into a weekly leaderboard. As you progress, you’ll earn promotion through Brilliant’s 10 league levels.

Meet the creator: CEO and cofounder Sue Khim wanted Brilliant to be a place where it’s OK to fail. “That’s the opposite of what you learned at school, which is: There’s a cost to every mistake,” Khim says. “But no matter what you do, you’re going to be given choices where there’s no obvious right answer, and you just have to figure it out.”