bare/gpt-5.1-codex-mini / tier-3-butt-hinge

```openscad
$fn = 64;

module leaf(side) {
    dx = 25;
    dy = 30;
    thickness = 2;
    base_x = side == "left" ? -dx : 0;
    knuckle_positions = side == "left" ? [-12, 0, 12] : [-6, 6];
    countersink_positions = [-8, 0, 8];
    
    difference() {
        union() {
            translate([base_x, -dy / 2, 0]) cube([dx, dy, thickness], center = false);
            for (pos = knuckle_positions)
                knuckle_segment(pos);
        }
        for (pos = knuckle_positions)
            knuckle_core(pos);
        for (pos = countersink_positions)
            countersink_hole(pos, side);
    }
}

module knuckle_segment(posY) {
    translate([0, posY, 1]) rotate([-90, 0, 0]) cylinder(h = 6, r = 4, center = true);
}

module knuckle_core(posY) {
    translate([0, posY, 1]) rotate([-90, 0, 0]) cylinder(h = 6, r = 2.3, center = true);
}

module countersink_hole(posY, side) {
    x = side == "left" ? -22 : 22;
    union() {
        translate([x, posY, 1]) cylinder(h = 1, r1 = 3, r2 = 1.6, center = false);
        translate([x, posY, -1]) cylinder(h = 5, r = 1.6, center = false);
    }
}

module hinge_pin() {
    translate([0, 0, 1]) rotate([-90, 0, 0]) cylinder(h = 32, r = 2, center = true);
}

union() {
    leaf("left");
    leaf("right");
    hinge_pin();
}
```