Flutter GridView not showing equally spaced items

Question

This is my code and it's supposed to create a uniform pattern:

GridView.builder(
          physics: const NeverScrollableScrollPhysics(),
          gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount 30),
          itemCount: 30 * 30,
          itemBuilder: (context, index) {
            return Container(
              decoration: BoxDecoration(
                  color: Colors.black, borderRadius: BorderRadius.circular(2)),
            );
          },
    ),

But it's an irregular pattern of lines and dots. I'm expecting uniform e.g. equidistant lines according to padding or equidistant dots according to the radius of container. Now all spacing values are zero there shouldn't be any line, it seems there's some other controlling factor.

I'm running this code on Desktop.