Codewars

Codewars skips lessons entirely and goes straight to practice: pick a kata, solve it in your language of choice, then compare your solution against other users' approaches once you pass, a format that rewards someone who already knows the basics and wants to sharpen problem-solving speed and pattern recognition rather than learn syntax for the first time.

Kata are ranked by difficulty and tagged by topic, so it's straightforward to filter for exactly the kind of problem you're weak on, algorithms, string manipulation, a specific language's quirks, and the built-in ranking system gamifies practice in a way that keeps regular users coming back. It fits someone who already has the fundamentals down, often preparing for technical interviews or just keeping skills sharp, more than a complete beginner who needs Codecademy's structured lessons first.