Most sites have a TOS: a terms of service. I, however, and not here to give you rules to follow: these are the rules that I follow, which I call the TOG (terms of goods).

• no TOS
• no gen AI (of course, unless I somehow make my own gen AI from scratch, but that isn't being used to make more
• no paying for anything, this is the web
• everything must be easy to mod (if you know JS). this means no WASM.
• no downloads: things must work in the browser
• all features must be baseline (if you use IE that's a you problem)
• NO ADS. EVER. They suck and would also make gravity simulator less performant. also idrc about money
• things must be able to work on a chromebook. it may take a bit of waiting to prevent crashing, but still tho.
• if it makes sense, MAKE IT INTERACTIVE. This is a problem I had with a LOT of simulations before I knew how to code, and with interactivity in all ways you'd want, you can learn a lot.
• also, things must be able to take user input and (usually) not NaN (aside from exetreme forces)
• simulations must be based on actual physics: if I ever make quantum mechanics, it's going to be actual QM
• oh also as little limits on simulations as makes sense: gravity simulator is boundless because it makes sense for space, and you can remove the left and right walls in the fluid simulator because why not
• you can use any of this without asking (as long as you give credit)