Nice logical map. The story, meh. ;-)

I guess I should add a button in there

oooh, I didn't account for that

I portaled the weighted cube into the exit area.

whered you get 2 cubes?

good to have a story :)
some suggestions:
the turret in the cage, next to the reflector cage.
I presume is in there for effect ?
why not have the turret facing the player & change the grating to glass.
it would also make more sense, to swap the weighted cube for the companion cube.
as at the moment, you use the weighted cube for most of the map.
& as a reward, add a button for it, at the exit.
(I got the sphere & 2 cubes, to the exit.
but only 2 buttons)

I had fun storming the castle, although on my first playthrough the Prince passed right through the last turret and dropped when it shot me. Felt like the Half-Life2 sniper when the grenade drops in his lap, "Sh*t!" I've seen that clipping error in a few other maps too. Worked fine on the 2nd try. Thanks for creating.