This looks like a really nice idea. I was considering something like this myself but I didn't know someone was already doing it. Looks like you have a bunch of users registered but I'm guessing something went wrong with the game library recently? As there is nothing in there.
Hey guys, issue 3 of the Independent Gamer is coming soon with....
Burning Thirst, Bastion, Transformice and of course as promised the top 3 games from Game Jam 5!
We also have an interview with the creators of Transformice and of course Josephs game theory section.
Oh ok I see what you're trying to do. Yeah thats a bit of a tricky one. I'm sure there is a way just not sure what it is. Would probably involve lots of lengthdir_x() lengthdir_y() calculations. With a bit of the box's image_angle thrown in for good measure. I'll have a think about this one and if I come up with anything I'll let you know.
So you want it spin at the same rate as the box sprite?
I think the best bet is to setup up a collision detection and when the 2 instances are in collision give the sprite that isn't the box the same image_angle of the box. You would need to get the ID of the box instance which is easy enough. Then its just image_angle=rotatingboxID.image_angle.
I hope I've explained that ok.