//+
Point(1) = {0, 0, 0, 0.02};
//+
Point(2) = {1, 0, 0, 0.02};
//+
Point(3) = {1, 1, 0, 0.01};
//+
Point(4) = {0.5, 1, 0, 0.01};
//+
Point(5) = {0, 1, 0, 0.02};
//+
Line(1) = {1, 2};
//+
Line(2) = {2, 3};
//+
Line(3) = {3, 4};
//+
Line(4) = {4, 5};
//+
Line(5) = {5, 1};
//+
Point(6) = {0.25, 0.25, 0, 0.05};
//+
Point(7) = {0.75, 0.25, 0, 0.02};
//+
Point(8) = {0.75, 0.75, 0, 0.02};
//+
Point(9) = {0.25, 0.75, 0, 0.02};
//+
Point(10) = {0.5, 0.5, 0, 0.01};
//+
Point(11) = {0.6, 0.5, 0, 0.01};
//+
Point(12) = {0.6, 0.6, 0, 0.01};
//+
Point(13) = {0.5, 0.6, 0, 0.01};
//+
Line(6) = {6, 7};
//+
Line(7) = {7, 8};
//+
Line(8) = {8, 9};
//+
Line(9) = {9, 6};
//+
Line(10) = {10, 11};
//+
Line(11) = {11, 12};
//+
Line(12) = {12, 13};
//+
Line(13) = {13, 10};
//+
Point(14) = {0.5, 0.9, 0.0, 0.1};
//+
Point(15) = {1.0, 0.95, 0.0, 0.01};
//+
Point(16) = {0.5, 0.95, 0.0, 0.01};
//+
Delete {
  Curve{2}; 
}
//+
Delete {
  Point{14}; 
}
//+
Line(14) = {2, 15};
//+
Line(15) = {15, 3};
//+
Line(16) = {15, 16};
//+
Line(17) = {16, 4};
//+
Curve Loop(1) = {16, 17, -3, -15};
//+
Plane Surface(1) = {1};
//+
Curve Loop(2) = {12, 13, 10, 11};
//+
Plane Surface(2) = {2};
//+
Curve Loop(3) = {8, 9, 6, 7};
//+
Plane Surface(3) = {2, 3};
//+
Curve Loop(4) = {4, 5, 1, 14, 16, 17};
//+
Plane Surface(4) = {3, 4};
//+
Physical Surface("area1", 18) = {2};
//+
Physical Surface("area2", 19) = {3};
//+
Physical Surface("area3", 20) = {4};
//+
Physical Surface("area4", 21) = {1};
//+
Physical Curve("left", 22) = {5};
//+
Physical Curve("right", 23) = {14, 15};
//+
Physical Curve("bottom", 24) = {1};
//+
Physical Curve("top_left", 25) = {4};
//+
Physical Curve("top_right", 26) = {3};

Mesh.RecombinationAlgorithm = 2;  // 或 3，尝试不同算法

Mesh.SubdivisionAlgorithm = 1;    // 细分后全四边形