Watch, don't memorize: I built a free visual way to finally understand data structures

You can read a hundred explanations of a linked list and still freeze when someone asks you to reverse one in an interview. You know the definition. You've seen the diagram. You've even solved the problem once, last Tuesday, with the tab still open. The problem isn't knowledge. It's that you've never watched one work. The gap between diagrams and intuition Every data structures resource falls into one of two buckets: Textbook mode : prose plus a static diagram. Here is a linked list. Each node points to the next node. Great. Now solve "reverse a linked list in O(n) time" and good luck. LeetCode mode : here are 3,000 problems. Memorize the patterns. Next. Both assume the intuition just shows up after enough reps. For a lot of us, it doesn't. Some people learn by watching the mechanism: the pointer that swings around, the array that silently doubles in size, the node that gets sifted up a heap. If you've never seen it happen, you're not debugging your solution. You're guessing. So I built the thing I wished existed. What I built learningto/pass is a free, interactive way to learn the classic interview curriculum: 16 topics from Big O through dynamic programming, where every concept is taught as a step-by-step animation before any code appears. Instead of "a binary search tree keeps smaller keys left and larger keys right," you insert keys one at a time and watch the tree grow, rebalance, and (sometimes) degenerate into a linked list. Which is its own lesson. The animations aren't decorative. Each topic's visuals are built around the exact moment students get stuck - how a hash table handles a collision, what a partition actually does in quicksort, why BFS radiates outward in rings. Then you code, in the browser, with no setup Watching isn't enough, so every topic has a practice section with real interview-style challenges. Python runs entirely in your browser via WebAssembly (Pyodide), so there is nothing to install: you write code, hit run, and see test case results