When I work on a simulation, the temptation is to start from how it should look and fix whatever looks wrong.

That’s the trap. Each defect gets its own patch, the patches don’t know about each other, and fixing one thing by hand quietly breaks something two patches away. You end up hand-correcting a world that has no idea what it’s supposed to obey.

So the first thing I write now is the rules. What does this world’s physics insist on? What is always true - things rest on the ground, wind moves everything it touches, a season changes what’s alive? Those go in as the foundation, before any scenery.

Then a defect stops being a surprise to squint at. It’s a rule being broken, and a broken rule is something you can check for.