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Every puzzle stays playable forever. Once a puzzle stops being the daily, its annotated solution unlocks: the reference answer, the mistake most solvers make, and a line-by-line walkthrough of why the compiler accepts one and rejects the other. Nothing is paywalled and nothing expires.

Par is the number of check-runs a competent solver should need, and it tracks the day of the week: Monday rebuilds something from the standard library at par 2, Friday asks for arithmetic on tuple lengths at par 5. If you are new to type-level TypeScript, work down the twelve concepts first — the Friday puzzles stop looking impossible surprisingly quickly.