We’ve featured a few different designs over the years; the walking-arm trebuchet is perhaps the most oddball of all. Video after the break.

Using trial and error, medieval engineers adjusted the trebuchet to make sure its missile hit the castle wall—and destroyed it. NOVA's science game, "Destroy the Castle," is very much like the ...

And he documented the entire build in a YouTube video which you can see below the break. The trebuchet is a type of catapult that was popular for use as a siege engine before gunpowder became a thing.