message: Stable but corners
diff: @@ -705,19 +705,15 @@ constexpr double SCALE = 8.0;
  struct Costa: public Surface<Costa>
  {
  Costa(Array<int> &BC, int o, int x, int y, int r, int d):
  - Surface(BC, o, r,
  - (x+1)*(y+1) - 4, // NVert
  - x*y - 4, // NElem
  - 0, // NBdrElem
  - d) { }
  - /*
  + Surface(BC, o, x, y, r, d) { }
  +
  void Prefix()
  {
  Array<int> v2v(GetNV());
  for (int i = 0; i < v2v.Size(); i++) { v2v[i] = i; }
  - const bool X = true;
  + const bool X = false;
  if (X) // horizontal border
  {
  for (int i = 1; i < nx; i++)
  @@ -730,7 +726,7 @@ struct Costa: public Surface<Costa>
  }
  }
  - const bool Y = true;
  + const bool Y = false;
  if (Y) // vertical border
  {
  for (int j = 1; j < ny; j++)
  @@ -792,7 +788,7 @@ struct Costa: public Surface<Costa>
  this->Print(mesh_ofs);
  exit(0);
  }
  - }*/
  + }
  void Create()
  {
  