Using auto margin to center an item in both the horizontal and vertical axes is tricky — unless that item is a grid item. Advertisements
Firefox Quantum: Developer Edition has a very useful tool to inspect the CSS grid layout in websites. Check out how to access and use it.
The answer is, a blueprint! I’m not kidding, this is the single best thing you could include in your Grid workflow (if you got one) that’ll make you master the gridding work