Unexpected size of chessboard in squares simple and complex examples

I am interested in creating an app for teaching the 3-check variant of chess and I have been looking for an appropriate framework. Your Dart/Flutter framework is very interesting. I am an experienced Delphi developer, but brand new to Dart/Flutter. I have been reading books on both Dart and Flutter to come up to speed. I am using the Microsoft Visual Studio Code IDE at the moment.

I was able to get both example programs to build and open in Windows 11. I didn't change any code. Visual Studio suggested that a few lines needed trailing commas and I allowed it to fix that syntax. The problem is that the chessboard and pieces are way too large (please see screenshots) and therefore you can only see the black pieces. I am hoping for a chessboard about the size of a "Lichess" chessboard. On the bottom of the simple example it says "Bottom overflowed by 1134 pixels" and at the bottom of the Complex Example after creating a game (I was slightly disappointed that 3-check didn't appear in the drop-down list but I imagine it can be added), it says "Bottom overflowed by 848 pixels." Visual studio Code seemed to indicate some kind of formatting error in the complex example (see screenshot) and I took a screenshot of something similar in the simple example.

Would you be able to point out what I should do to fix this?
Thank you.