$fn=64;

// --- Parameters ---
num_slots = 12;
slot_spacing = 30;
shelf_depth = 45;
shelf_thickness = 12;
backplate_height = 60;
backplate_thickness = 8;
wedge_width = 6;

rack_length = (num_slots * slot_spacing) + 10;

// Mounting hole parameters
mount_hole_dia = 5;
mount_hole_head = 10;

// --- Main Model ---
difference() {
    // 1. Solid Body
    union() {
        // Backplate
        cube([rack_length, backplate_thickness, backplate_height]);
        
        // Shelf
        translate([0, 0, backplate_height - shelf_thickness])
            cube([rack_length, shelf_depth + backplate_thickness, shelf_thickness]);

        // Support Wedges (Ends and evenly distributed)
        for (x = [
            0, 
            (4 * slot_spacing) + 5 - wedge_width/2, 
            (8 * slot_spacing) + 5 - wedge_width/2, 
            rack_length - wedge_width
        ]) {
            translate([x, backplate_thickness - 0.1, 0])
                support_wedge(wedge_width, shelf_depth - 5, backplate_height - shelf_thickness + 0.1);
        }
    }

    // 2. Subtractions (Slots and Holes)
    
    // Screwdriver Slots (Graduated sizes for a complete set)
    for (i = [1 : num_slots]) {
        // Calculate graduated sizes: 4 small, 4 medium, 4 large
        hole_dia = 10 + floor((i - 1) / 4) * 4;   // 10mm, 14mm, 18mm
        slot_width = 6 + floor((i - 1) / 4) * 2;  // 6mm, 8mm, 10mm
        
        x_pos = (i - 0.5) * slot_spacing + 5;
        y_pos = backplate_thickness + shelf_depth - 18;
        z_pos = backplate_height - shelf_thickness - 1;
        
        translate([x_pos, y_pos, z_pos]) {
            // Main resting hole
            cylinder(h = shelf_thickness + 2, d = hole_dia);
            
            // Front U-slot opening
            translate([-slot_width/2, 0, 0])
                cube([slot_width, 40, shelf_thickness + 2]);
                
            // Top countersink/chamfer for easy insertion
            translate([0, 0, shelf_thickness + 1 - 3])
                cylinder(h = 3.1, d1 = hole_dia, d2 = hole_dia + 6);
        }
    }

    // Wall Mounting Holes
    mount_y = backplate_height - shelf_thickness - 20;
    for (x = [20, rack_length / 2, rack_length - 20]) {
        translate([x, backplate_thickness + 1, mount_y])
            rotate([90, 0, 0]) {
                // Screw shaft
                cylinder(h = backplate_thickness + 2, d = mount_hole_dia);
                // Screw head countersink
                translate([0, 0, backplate_thickness - 3])
                    cylinder(h = 4.1, d = mount_hole_head);
            }
    }
}

// --- Helper Modules ---
module support_wedge(w, d, h) {
    hull() {
        // Back wall alignment
        cube([w, 0.1, h]);
        // Top shelf alignment
        translate([0, 0, h - 0.1]) 
            cube([w, d, 0.1]);
    }
}