$fn = 64;

// --- Parameters ---
num_slots = 3;
slot_spacing = 45;
block_depth = 40;
block_height = 25;

slot_width = 12;      // Width of the main slot
slot_depth = 25;      // Depth of the slot
spring_thick = 2.5;   // Thickness of the flexible cantilever arms
relief_width = 3;     // Width of the flex clearance
bump_radius = 2.5;    // Size of the gripping bump

hole_dia = 4.5;       // Screw hole diameter (M4)
head_dia = 8.5;       // Screw head diameter
head_depth = 17;      // Depth of screw counterbore

corner_r = 3;
block_width = num_slots * slot_spacing;

// --- Main Assembly ---
difference() {
    // Extrude the 2D profile into the 3D block
    linear_extrude(block_height) {
        difference() {
            // Base rounded block
            hull() {
                translate([corner_r, corner_r]) circle(r=corner_r);
                translate([block_width - corner_r, corner_r]) circle(r=corner_r);
                translate([corner_r, block_depth - corner_r]) circle(r=corner_r);
                translate([block_width - corner_r, block_depth - corner_r]) circle(r=corner_r);
            }
            
            // Cut out each spring slot
            for (i = [0 : num_slots - 1]) {
                translate([slot_spacing/2 + i * slot_spacing, 0]) {
                    slot_profile();
                }
            }
        }
    }
    
    // Mounting holes (placed between slots)
    for (i = [1 : num_slots - 1]) {
        translate([i * slot_spacing, 15, -1]) {
            // Through hole
            cylinder(h = block_height + 2, d = hole_dia);
            // Counterbore for screw head
            translate([0, 0, block_height - head_depth + 1]) 
                cylinder(h = head_depth + 2, d = head_dia);
        }
    }
}

// --- Modules ---
module slot_profile() {
    sw = slot_width;
    sd = slot_depth;
    st = spring_thick;
    rw = relief_width;
    
    difference() {
        union() {
            // Main central slot
            translate([-sw/2, block_depth - sd]) 
                square([sw, sd + 1]);
            
            // Rounded bottom of the slot
            translate([0, block_depth - sd]) 
                circle(d=sw);
            
            // Left relief cut and rounded bottom
            translate([-sw/2 - st - rw, block_depth - sd - 4]) 
                square([rw, sd + 5]);
            translate([-sw/2 - st - rw/2, block_depth - sd - 4]) 
                circle(d=rw);
            
            // Right relief cut and rounded bottom
            translate([sw/2 + st, block_depth - sd - 4]) 
                square([rw, sd + 5]);
            translate([sw/2 + st + rw/2, block_depth - sd - 4]) 
                circle(d=rw);
            
            // Entry chamfer/flare to guide tools in
            polygon([
                [-sw/2, block_depth - 4],
                [sw/2, block_depth - 4],
                [sw/2 + 5, block_depth + 1],
                [-sw/2 - 5, block_depth + 1]
            ]);
        }
        
        // Gripping bumps (kept solid by subtracting them from the cutout space)
        translate([-sw/2, block_depth - sd + 10]) 
            circle(r=bump_radius);
        translate([sw/2, block_depth - sd + 10]) 
            circle(r=bump_radius);
    }
}