$fn=64;

// --- Parameters ---
total_width = 100;      // Total width of the insert (X axis)
total_length = 150;     // Total length of the insert (Y axis)
height = 20;            // Total height of the grid
wall_thickness = 1.6;   // Thickness of the divider walls
columns = 4;            // Number of compartments in X axis
rows = 3;               // Number of compartments in Y axis
has_base = false;       // Set to true to include a solid bottom tray
base_thickness = 1.6;   // Thickness of the bottom base (if has_base is true)

module grid_insert() {
    // Calculate individual compartment dimensions
    comp_w = (total_width - (wall_thickness * (columns + 1))) / columns;
    comp_l = (total_length - (wall_thickness * (rows + 1))) / rows;
    
    // Z-axis cut logic to ensure clean manifold subtraction
    z_offset = has_base ? base_thickness : -1;
    cut_height = has_base ? height - base_thickness + 1 : height + 2;

    difference() {
        // Main solid block
        cube([total_width, total_length, height]);
        
        // Subtract compartments
        for (x = [0 : columns - 1]) {
            for (y = [0 : rows - 1]) {
                x_pos = wall_thickness + x * (comp_w + wall_thickness);
                y_pos = wall_thickness + y * (comp_l + wall_thickness);
                
                translate([x_pos, y_pos, z_offset])
                    cube([comp_w, comp_l, cut_height]);
            }
        }
    }
}

grid_insert();