Brilliant

Brilliant took the opposite approach from video lectures — they built interactive problem-solving courses that teach math, science, and computer science through doing, not watching. Each lesson is a series of puzzles that build on each other, making abstract concepts click through hands-on experimentation. Their courses on neural networks, quantum mechanics, and algorithms make intimidating subjects genuinely approachable. At $25/month (or $150/year), it's the best platform for building quantitative thinking skills from scratch.