It has a couple hundred questions. I've sampled a few of
them. Most are of the following style: show a piece of
lecture/demonstration apparatus and ask what the outcome
will be. A qualitative answer suffices, i.e. no detailed
numerical computation is required.
I'm not sure I'd call them riddles or puzzles, just questions.
They're easy if you understand physics at the freshman intro
level (mechanics, electrostatics, magnetostatics, et cetera).
The approved answer is also available, along with a moderate
amount of explanation.