Hymnle plays you the opening of a national anthem, one second at first, and you guess which country it belongs to. Every wrong guess or skip lets you hear more of it.
They are performances by the United States Navy Band, which are in the public domain, hosted on Wikimedia Commons.
Yes. In hard mode there is no skipping and no hints: only wrong guesses unlock more of the anthem.
Yes. All four games are free to play in any web browser, with no account or download needed.
Each game has one new daily puzzle, and it unlocks at midnight in your own time zone. Everyone in the world gets the same country on the same day.
Yes. Every game has a practice mode with unlimited random rounds, and practice rounds earn XP towards levels.