deriveTrail function
Derives a gradient of trail colors from a single bright color.
Each step is progressively dimmed (via Color.dim) to create the falling trail effect behind the scanner head.
Implementation
List<Color> deriveTrail(Color bright, {int steps = 6}) {
final result = <Color>[bright];
var current = bright;
for (var i = 1; i < steps; i++) {
current = current.dim;
result.add(current);
}
return result;
}