$fn = 64;

// --- Parametric Dimensions ---
length = 120;
width = 80;
height = 60;
wall_thickness = 2.5; // Sturdy walls for 1kg capacity
corner_radius = 6;
lip_width = 3;        // Reinforcing top lip width
lip_height = 4;       // Reinforcing top lip height

// --- Derived Dimensions ---
inner_length = length - 2 * wall_thickness;
inner_width = width - 2 * wall_thickness;
inner_radius = max(0.1, corner_radius - wall_thickness);

// --- Modules ---
module rounded_box(l, w, h, r) {
    hull() {
        translate([r, r, 0]) cylinder(r=r, h=h);
        translate([l-r, r, 0]) cylinder(r=r, h=h);
        translate([r, w-r, 0]) cylinder(r=r, h=h);
        translate([l-r, w-r, 0]) cylinder(r=r, h=h);
    }
}

// --- Main Object ---
difference() {
    // Outer Shell
    union() {
        // Main bin body
        rounded_box(length, width, height, corner_radius);
        
        // Top reinforcing lip for strength
        translate([-lip_width, -lip_width, height - lip_height])
            rounded_box(length + 2 * lip_width, width + 2 * lip_width, lip_height, corner_radius + lip_width);
    }
    
    // Inner Hollow Cutout
    // Height is increased slightly to ensure a clean manifold cut at the top
    translate([wall_thickness, wall_thickness, wall_thickness])
        rounded_box(inner_length, inner_width, height + 1, inner_radius);
}