$fn=64;

// --- Parameters ---
columns = 5;
rows = 4;           // 5 x 4 = 20 paint tubes
hole_diameter = 26; // 26mm fits standard miniature paint bottles and standard acrylic tubes
hole_depth = 22;    // Depth of the holder
wall_thickness = 2; // Thickness of the plastic walls
base_thickness = 2; // Thickness of the bottom floor

// --- Calculated Variables ---
outer_diameter = hole_diameter + (wall_thickness * 2);
// Spacing creates a 1.5mm overlap between cylinders to fuse them into a single solid body
spacing = outer_diameter - 1.5; 

// --- Geometry ---
difference() {
    // Main body: A grid of overlapping solid cylinders
    union() {
        for (c = [0 : columns - 1]) {
            for (r = [0 : rows - 1]) {
                translate([c * spacing, r * spacing, 0])
                    cylinder(h = hole_depth + base_thickness, d = outer_diameter);
            }
        }
    }
    
    // Hollow out the cylinders to create the tube holders
    for (c = [0 : columns - 1]) {
        for (r = [0 : rows - 1]) {
            translate([c * spacing, r * spacing, base_thickness])
                // Add 1 to height to ensure a clean manifold cut through the top surface
                cylinder(h = hole_depth + 1, d = hole_diameter);
        }
    }
}