1. Click the Run button.

2. In the code, change the Row to a Column, and run again.

Axis size and alignment

So far, the BlueBox widgets have been squished together
(either to the left or at the top of the UI Output).
You can change how the BlueBox widgets are spaced
out using the axis size and alignment properties.

mainAxisSize property

Row and Column occupy all of the space on their main axes.
If the combined width of their children is
less than the total space on their main axes,
their children are laid out with extra space.

Row and Column only occupy enough space on their main axes
for their children. Their children are laid out without extra space
and at the middle of their main axes.