$fn = 64;

// --- Parameters ---
height = 100;               // Total height of the pen holder (mm)
outer_radius = 32;          // Outer circumscribed radius of the hexagon (mm)
wall_thickness = 2.5;       // Thickness of the walls (mm)
base_thickness = 3.0;       // Thickness of the solid bottom base (mm)
twist_angle = 60;           // Total twist angle for a modern look (degrees)

// --- Geometry ---
difference() {
    // 1. Solid outer hexagonal body
    linear_extrude(height = height, twist = twist_angle, slices = 120) {
        circle(r = outer_radius, $fn = 6);
    }
    
    // 2. Hollow inner cavity
    difference() {
        // Extrude the inner profile slightly taller to ensure a clean cut at the top opening.
        // The twist rate is scaled to perfectly match the outer body's twist at any given Z height.
        linear_extrude(
            height = height + 1, 
            twist = twist_angle * ((height + 1) / height), 
            slices = 122
        ) {
            circle(r = outer_radius - wall_thickness, $fn = 6);
        }
        
        // 3. Mask out the bottom portion of the inner cavity to leave a solid base
        // This cube exactly covers from Z = -2 up to Z = base_thickness
        translate([0, 0, base_thickness / 2 - 1]) {
            cube([outer_radius * 3, outer_radius * 3, base_thickness + 2], center = true);
        }
    }
}