Algodoo

Tried to make an asteroid/planet thingy with heat from impacts and compression
set the parameters on the little menu guy and mash the go button when you're ready (menu guy doesnt work when its paused).
it'll start off as a swarm of grey dots that slowly merge into blobs that collide and change colors. set attraction to 0 and turn gravity on for lava mode
It aint perfect but it mostly does the thing I was wanting it to do