How to make flutter web size like app size

Question

I am developing a flutter app and try to run it on web too. How do you make the size of a web app like a phone app? I saw some web app has the fixed size of phone app like following;https://i.sstatic.net/2J36E.jpg

Answer 1

This will make it stay in a 16:9 ratio but will scale everything down if needed.

FittedBox(
    fit: BoxFit.scaleDown,
    child: Container(
        width: 0.5625*height,
        height: height,
        child: Container(),
    ),
),