$fn=64;

// --- Parameters ---
cols = 4;
rows = 3;
cell_pitch = 40;
cell_bottom_width = 30;
cell_top_width = 41.5; 
cell_depth = 45;
wall_thickness = 1.5;

lip_width = 2;
lip_height = 3;

drain_hole_dia = 8;
channel_width = 6;
channel_depth = 3;

// --- Main Assembly ---
translate([-(cols-1)*cell_pitch/2, -(rows-1)*cell_pitch/2, 0])
    tray();

// --- Modules ---
module tray() {
    difference() {
        union() {
            // Main cell bodies
            for(x=[0:cols-1], y=[0:rows-1]) {
                translate([x*cell_pitch, y*cell_pitch, 0])
                    tapered_cell(cell_top_width, cell_bottom_width, cell_depth, 0);
            }
            
            // Outer reinforced lip
            translate([-cell_pitch/2 - lip_width, -cell_pitch/2 - lip_width, cell_depth - lip_height])
                cube([cols*cell_pitch + 2*lip_width, rows*cell_pitch + 2*lip_width, lip_height]);
        }
        
        // Cell inner voids
        for(x=[0:cols-1], y=[0:rows-1]) {
            inner_top = cell_top_width - 2*wall_thickness;
            inner_bot = cell_bottom_width - 2*wall_thickness;
            
            translate([x*cell_pitch, y*cell_pitch, wall_thickness])
                tapered_cell(inner_top, inner_bot, cell_depth, 1);
            
            // Drainage holes
            translate([x*cell_pitch, y*cell_pitch, -1])
                cylinder(h=wall_thickness+2, d=drain_hole_dia);
        }
        
        // Interconnected water channels (Bottom grooves)
        // X-axis channels
        for(y=[0:rows-1]) {
            translate([-cell_pitch, y*cell_pitch - channel_width/2, -0.1])
                cube([cols*cell_pitch + cell_pitch, channel_width, channel_depth + 0.1]);
        }
        
        // Y-axis channels
        for(x=[0:cols-1]) {
            translate([x*cell_pitch - channel_width/2, -cell_pitch, -0.1])
                cube([channel_width, rows*cell_pitch + cell_pitch, channel_depth + 0.1]);
        }
    }
}

module tapered_cell(top_w, bot_w, h, extra) {
    hull() {
        translate([0, 0, -extra])
            cube([bot_w, bot_w, 0.01], center=true);
        translate([0, 0, h + extra])
            cube([top_w, top_w, 0.01], center=true);
    }
}