Algodoo

It appears that physics is calculated before objects are deleted by killer objects.

I actually didn't expect this because killer objects kill objects before scripts are run (hence why you can't use onCollide when an object is killed by a killer object!), so that's fascinating!

huh. that's both odd and cool

It goes to the right because it is spinning in a clockwise direction when it comes in contact with the plane. Think of it like a car tire that will move in the direction that it spins while it contacts the road. Even though you do not have gravity enabled, the object has some initial downward velocity before it contacts the plane. When it contacts the killer plane, only a few of the boxes get stripped off the outer edge of the group, causing the square group of boxes becoming rounded. Very quickly after contacting the plane, the velocity of the group switches from vertical to horizontal and no more boxes get stripped off the group by the killer plane.

My explanation may be a little verbose but that's just me!

Ok.