bare-low/gpt-5.6-sol / tier-2-offset-handle-mug

```openscad
$fn = 128;

// Mug dimensions
outer_diameter = 80;
inner_diameter = 70;
mug_height     = 90;
bottom_thickness = 6;

// Handle dimensions
handle_depth = 12;
handle_center_z = mug_height / 2;

// Inner D-shaped opening: 25 mm wide × 30 mm high
inner_radius = 15;
inner_straight_length = 10;
inner_base_x = 43;
inner_center_x = inner_base_x + inner_straight_length;

// Handle wall thickness
handle_wall = 6;
outer_radius = inner_radius + handle_wall;
outer_base_x = 37;
outer_center_x = inner_center_x;

arc_steps = 64;

function d_shape_points(base_x, center_x, center_z, radius) =
    concat(
        [[base_x, center_z + radius]],
        [
            for (i = [0 : arc_steps])
                let(a = 90 - 180 * i / arc_steps)
                [
                    center_x + radius * cos(a),
                    center_z + radius * sin(a)
                ]
        ],
        [[base_x, center_z - radius]]
    );

module mug_body() {
    difference() {
        cylinder(d = outer_diameter, h = mug_height);

        translate([0, 0, bottom_thickness])
            cylinder(
                d = inner_diameter,
                h = mug_height - bottom_thickness + 1
            );
    }
}

module handle() {
    rotate([90, 0, 0])
        linear_extrude(height = handle_depth, center = true, convexity = 10)
            difference() {
                polygon(
                    points = d_shape_points(
                        outer_base_x,
                        outer_center_x,
                        handle_center_z,
                        outer_radius
                    )
                );

                polygon(
                    points = d_shape_points(
                        inner_base_x,
                        inner_center_x,
                        handle_center_z,
                        inner_radius
                    )
                );
            }
}

union() {
    mug_body();
    handle();
}
```