bare-high/gpt-5.6-luna / tier-3-butt-hinge

```openscad
$fn = 96;

// Dimensions
leaf_length = 30;
leaf_width  = 25;
leaf_thickness = 2;

knuckle_length = 6;
knuckle_outer_d = 8;
knuckle_inner_d = 4.6;

pin_d = 4;
pin_length = 32;

hole_d = 3.2;
countersink_d = 6;
countersink_depth = 1;

// The leaf overlaps the knuckle slightly for a connected solid.
// Each leaf remains exactly 25 mm wide.
left_leaf_x0  = -28;
right_leaf_x0 = 3;

hole_y = [7, 15, 23];

module countersunk_hole(x, y) {
    translate([x, y, -leaf_thickness / 2 - 0.01])
        cylinder(h = leaf_thickness + 0.02, d = hole_d);

    translate([x, y, 0])
        cylinder(
            h = countersink_depth,
            r1 = hole_d / 2,
            r2 = countersink_d / 2
        );
}

module leaf_plate(x0, hole_x) {
    difference() {
        translate([x0, 0, -leaf_thickness / 2])
            cube([leaf_width, leaf_length, leaf_thickness]);

        for (y = hole_y)
            countersunk_hole(hole_x, y);
    }
}

module knuckle(y0) {
    difference() {
        translate([0, y0, 0])
            rotate([-90, 0, 0])
                cylinder(h = knuckle_length, d = knuckle_outer_d);

        translate([0, y0 - 0.1, 0])
            rotate([-90, 0, 0])
                cylinder(h = knuckle_length + 0.2, d = knuckle_inner_d);
    }
}

module left_leaf_assembly() {
    union() {
        leaf_plate(left_leaf_x0, -15.5);

        knuckle(0);
        knuckle(12);
        knuckle(24);
    }
}

module right_leaf_assembly() {
    union() {
        leaf_plate(right_leaf_x0, 15.5);

        knuckle(6);
        knuckle(18);
    }
}

module hinge_pin() {
    translate([0, -1, 0])
        rotate([-90, 0, 0])
            cylinder(h = pin_length, d = pin_d);
}

color([0.42, 0.44, 0.47])
    left_leaf_assembly();

color([0.48, 0.50, 0.53])
    right_leaf_assembly();

color([0.72, 0.74, 0.78])
    hinge_pin();
```