No, It's not a monster, I think that someone made a similar rolling boulder effect a long time ago. Haven't looked the sources but I guess it's the same idea. So this is nothing new actually.
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Static block is just a blocker-object and moving block is a projectile(I have 4 of these pointing at different directions so the projectile can have the same facing as the static block). And I also have a party.onMove hook which prevents the party collide with block...etc. I made a smaller block too, which can move through doors. This way it's possible to make any static object moveable, or even pushable.
Thanks, all of you. One small gotcha is that if a monster and a block is moving to the same tile at the same time, the monster will go right through of the block and the block will stop. But I think that it can be fixed so that the monster is killed and the block is respawned.
Same goes with party of course, but in current implementation the whole party is killed if it's hit by a moving block.
I made another video with a dragon statue which demonstrates the interaction with doors. And I'm going to release this with the new version of my framework, and as a teaser: making a object moveable is easy as this:
fw_makeMoveable('dragon_statue',"assets/models/env/dragon_statue.fbx")
Then you can just place a dragon statue in your dungeon and you can move it by calling moveobj.move(dragon_statue_id,dir)