MorphPiece.morphable constructor
A morph-source piece: the group installs a MorphTag around the content itself and plays the flight neck whenever a flight is launched with this piece's id.
Implementation
// The child is required BY TYPE: the MorphTag that gives the piece
// its flight identity wraps the child, so a childless piece would
// register no tag and showMorph*(from: id) could never find the
// source.
const MorphPiece.morphable({
required this.id,
required this.rect,
this.radius = 20,
this.solid = true,
this.bumpScale = 0.6,
this.bumpRecoil = 140,
this.channel,
required Widget this.child,
}) : morphable = true;