$fn=64;

// --- Parameters ---
base_width = 150;
base_length = 150;
base_height = 8;
corner_radius = 4;

recess_width = 130;
recess_length = 130;
recess_depth = 2;

magnet_hole_diameter = 5.2; // Sized for 5mm magnets
magnet_hole_depth = 2.5;
magnet_offset = 15;

// --- Main Model ---
difference() {
    // Solid Foundation Base
    rounded_cube(base_width, base_length, base_height, corner_radius);
    
    // Top Recess for Building Placement
    translate([0, 0, base_height - recess_depth + 0.01])
        rounded_cube(recess_width, recess_length, recess_depth + 0.1, corner_radius);
        
    // Bottom Magnet/Peg Holes for Modularity
    for (x = [-1, 1]) {
        for (y = [-1, 1]) {
            translate([
                x * (base_width/2 - magnet_offset), 
                y * (base_length/2 - magnet_offset), 
                -0.01
            ])
            cylinder(d=magnet_hole_diameter, h=magnet_hole_depth + 0.01);
        }
    }
}

// --- Modules ---
module rounded_cube(w, l, h, r) {
    hull() {
        for (x = [-w/2 + r, w/2 - r]) {
            for (y = [-l/2 + r, l/2 - r]) {
                translate([x, y, 0])
                    cylinder(r=r, h=h);
            }
        }
    }
}