Allow me to recommend The Powder Toy[0]. It is to date, as far as I can tell, The most advanced falling sand game available, aside from maybe Noita, though the focus there is quite different from most falling sand games. It has hundreds of different elements to play with. It simulates air pressure and can with the toggle of a button simulate ambient heat, water pressure, and newtonian gravity. People have built everything from bombs to CPUs in it.

Disclaimer: I did some minor development work on TPT and am involved in the community. Still though, great game.

[0] https://powdertoy.co.uk/

Absolutely! I mentioned it in my first post. Great implementation and a good blog post about how it's made.