Falling Sand 2D + 3D is a falling-sand sandbox built 100% with Geometry Nodes: a 2D pixel canvas and a 3D voxel box with 12 reacting elements (sand, water, stone, wood, oil, lava, fire, smoke, steam, acid, gunpowder and an eraser). Press Play and paint with brush objects while it runs. No add-on, no Python. Works in Blender 4.5 LTS and 5.x.

Documentation: blenderprocedural.github.io/falling-sand/docs.html