extrudedBox function
A box with one face pushed out and the top of the tower narrowed.
Two extrusions rather than one, because a single one is symmetric enough to look right with a wall missing; the second gives the shape a silhouette that only closes if every wall of both is there.
Implementation
EditMesh extrudedBox() {
final mesh = ParametricCuboid().toEditMesh();
// Face 2 is the +Y one in the table the cuboid shares with the engine, so
// the tower goes up — which is the direction a viewport frames best.
final top = Selection.of(ElementLevel.face, <int>[2]);
mesh.beginStep();
extrudeFaces(mesh, top, distance: 0.7);
extrudeFaces(mesh, top, distance: 0.5);
scaleSelection(mesh, top, by: Vector3(0.45, 0.45, 0.45));
mesh
..endStep()
..clearJournal();
return mesh;
}