There was a time when I treated layout like it started at display: flex;. If something wasn’t aligned, spaced, or distributed exactly the way I imagined, I didn’t pause to understand what the browser was already doing. I just reached for Flexbox. It felt like leveling up. Normal document flow, on the other hand, felt like the starter dungeon. Functional. Necessary. But not where the “real” mechanics lived. That assumption was wrong. Because CSS flow isn’t the tutorial. It’s the physics engine. Flexbox is a powerful positioning spell layered on top of it. And if you don’t understand the world’s physics, you end up burning high-level slots to solve low-level…