$fn = 64;

// --- Parameters ---
projection = 25;         // Total projection from wall
width = 12;              // Width of the hook
thickness = 5;           // Thickness of the backplate and arm
hook_inner_r = 6;        // Inner radius of the hook curve
hook_outer_r = hook_inner_r + thickness;
backplate_top = 40;      // Height above the arm
backplate_bottom = -15;  // Depth below the arm
hole_dia = 4;            // Screw hole diameter
cs_dia = 8;              // Countersink diameter
fillet_r = 4;            // Corner fillet radius

// --- 3D Model ---
difference() {
    // Main Body
    linear_extrude(height = width) {
        union() {
            // Backplate main body
            translate([0, backplate_bottom + thickness/2])
                square([thickness, backplate_top - backplate_bottom - thickness]);

            // Backplate rounded ends
            translate([thickness/2, backplate_top - thickness/2]) circle(d=thickness);
            translate([thickness/2, backplate_bottom + thickness/2]) circle(d=thickness);

            // Straight arm
            arm_length = projection - hook_outer_r;
            square([arm_length, thickness]);

            // Curved hook part
            translate([arm_length, hook_outer_r]) {
                difference() {
                    circle(r=hook_outer_r);
                    circle(r=hook_inner_r);
                    // Remove left half to form the hook
                    translate([-hook_outer_r-1, -hook_outer_r-1])
                        square([hook_outer_r+1, hook_outer_r*2+2]);
                }
            }

            // Rounded tip for the hook
            translate([arm_length, hook_outer_r + hook_inner_r + thickness/2])
                circle(d=thickness);

            // Top internal fillet (tension support)
            translate([thickness, thickness]) difference() {
                square([fillet_r, fillet_r]);
                translate([fillet_r, fillet_r]) circle(r=fillet_r);
            }

            // Bottom internal fillet (compression support)
            translate([thickness, 0]) difference() {
                translate([0, -fillet_r]) square([fillet_r, fillet_r]);
                translate([fillet_r, -fillet_r]) circle(r=fillet_r);
            }
        }
    }

    // Top Screw Hole
    translate([-1, backplate_top - 8, width/2])
        rotate([0, 90, 0])
        cylinder(d=hole_dia, h=thickness+2);

    // Top Countersink
    translate([thickness - 2, backplate_top - 8, width/2])
        rotate([0, 90, 0])
        cylinder(d1=hole_dia, d2=cs_dia, h=2.01);

    // Bottom Screw Hole
    translate([-1, backplate_bottom + 8, width/2])
        rotate([0, 90, 0])
        cylinder(d=hole_dia, h=thickness+2);

    // Bottom Countersink
    translate([thickness - 2, backplate_bottom + 8, width/2])
        rotate([0, 90, 0])
        cylinder(d1=hole_dia, d2=cs_dia, h=2.01);
}