Flutter Icons

Flutter via Material Design has access to a hundreds of monochrome icons.

Check them out here: https://docs.flutter.io/flutter/material/Icons-class.html

Snippet example:

Widget buttonSection = Container(
  child: Row(
    mainAxisAlignment: MainAxisAlignment.spaceEvenly,
    children: [
      buildButtonColumn(Icons.check_box, 'Check Answer'),
      buildButtonColumn(Icons.help, 'Give Hint'),
      buildButtonColumn(Icons.visibility, 'Give Up'),
    ],
  ),
);

Modified the flutter.io Top Lakes examples as shown: