//container
Container(
  width: 200.0,
  height: 200.0,
  color: Colors.green,
  margin: EdgeInsets.symmetric(vertical: 20.0),
);

// Color 
Color _color = Colors.green;
_color = Color.fromRGBO(random.nextInt(256), random.nextInt(256), random.nextInt(256), 1,);

//border Radius
BorderRadiusGeometry _borderRadius = BorderRadius.circular(8);

decoration: BoxDecoration(
  color: _color,
  borderRadius: _borderRadius,
),

//Icon
Icon(Icons.play_arrow)

//font size
final _biggerFont = const TextStyle(fontSize: 18.0);
final _smallFont = const TextStyle(fontSize: 12.0);

//padding
const EdgeInsets.all(16.0)
  
//animation param
// Define how long the animation should take.
duration: Duration(seconds: 1),
Duration(milliseconds: 500)
// Provide an optional curve to make the animation feel smoother.
curve: Curves.fastOutSlowIn,

//text style
Text('example', 
     style: TextStyle(
       color: Colors.red,
       fontSize: 18.0,
       decorationStyle: TextDecorationStyle.dashed,
       bakcgroudColor: Colors.yellow,
       height: 1.0,
       fontWeight: FontWeight.bold
     ),
    )