union() {
    linear_extrude(height=20)
        polygon([
            [12, 30],
            [11, 29],
            [11, 28],
            [22, 12],
            [22, 11],
            [21, 10],
            [2,  10],
            [1,  9.7],
            [0,  8 ],
            [0,  0 ],
            [64, 0 ],
            [64, 8 ],
            [63.7, 9.7],
            [63, 10],
            [44, 10],
            [42.3, 10.3],
            [42, 12],
            [53.7, 28.3],
            [54, 29.7],
            [53, 30],
        ]);
        
    difference() {
        polyhedron(
            points = [
                [0,0,0],   // 索引 0: V0
                [0,0,20],  // 索引 1: V1
                [64,0,20], // 索引 2: V2
                [64,0, 0],  // 索引 3: V3
                [64,-60,0],// 索引 4: V4
                [0, -60,0]  // 索引 5: V5
            ],
            faces = [
                // 修正后的 faces 列表：
                [0, 5, 4, 3], // Bottom (Z=0) - 确认顺序，从外部看顺时针
                [1, 0, 3, 2], // Face at Y=0 (Vertical Front) - 确认顺序，从外部看顺时针
                [1, 2, 4, 5], // Top (Sloped) - 确认顺序，从外部看顺时针
                [1, 5, 0],   // Left Side (X=0, Triangle) - 确认顺序，从外部看顺时针
                [2, 3, 4]    // Right Side (X=64, Triangle) - 确认顺序，从外部看顺时针
            ]
        );
        translate([0, -60, 0])
            difference() {
                cube(4);
                translate([4,4,0])
                    cylinder(h=4, r=4);
            }

        translate([60, -60, 0])
            difference() {
                cube(4);
                translate([0,4,0])
                    cylinder(h=4, r=4);
            }
    }
}