Read a snippet, name its time and space complexity, then check the reasoning behind the bound.
Unlike the Big O quiz, there's real code on screen: nested loops, recursion, hidden linear work inside a loop body. You pick both the time and the space bound, then read why. Snippets are in Python, JavaScript, and Java. Cards are drawn with spaced repetition, so the ones you miss come back sooner and the ones you know back off. Progress is kept in your browser.