$fn = 64;

// --- Parameters ---
riser_height = 75;          // Total height of the riser body
base_size = 40;             // Width/Depth of the top and bottom platforms
base_thickness = 5;         // Thickness of the solid top/bottom platforms
transition_height = 10;     // Height of the chamfered overhangs (for 3D printability)
pillar_size = 20;           // Width/Depth of the central support pillar

peg_spacing = 24;           // Distance between interlocking pegs
peg_diameter = 4.0;         // Diameter of the top pegs
peg_height = 4.0;           // Height of the top pegs
clearance = 0.4;            // Tolerance for the bottom sockets

// --- Main Module ---
module figure_stage_riser() {
    difference() {
        union() {
            // Bottom Base
            translate([0, 0, base_thickness / 2])
                cube([base_size, base_size, base_thickness], center=true);

            // Bottom Chamfered Transition (Printable without supports)
            hull() {
                translate([0, 0, base_thickness - 0.05])
                    cube([base_size, base_size, 0.1], center=true);
                translate([0, 0, base_thickness + transition_height])
                    cube([pillar_size, pillar_size, 0.1], center=true);
            }

            // Central Pillar
            translate([0, 0, riser_height / 2])
                cube([pillar_size, pillar_size, riser_height - 2*base_thickness - 2*transition_height + 0.2], center=true);

            // Top Chamfered Transition
            hull() {
                translate([0, 0, riser_height - base_thickness - transition_height])
                    cube([pillar_size, pillar_size, 0.1], center=true);
                translate([0, 0, riser_height - base_thickness + 0.05])
                    cube([base_size, base_size, 0.1], center=true);
            }

            // Top Base
            translate([0, 0, riser_height - base_thickness / 2])
                cube([base_size, base_size, base_thickness], center=true);

            // Top Interlocking Pegs
            for(x = [-1, 1], y = [-1, 1]) {
                translate([x * peg_spacing/2, y * peg_spacing/2, riser_height])
                    cylinder(h=peg_height, d=peg_diameter);
            }
        }

        // Bottom Interlocking Sockets
        for(x = [-1, 1], y = [-1, 1]) {
            translate([x * peg_spacing/2, y * peg_spacing/2, -1])
                cylinder(h=peg_height + 1.5, d=peg_diameter + clearance);
        }
    }
}

// --- Render ---
figure_stage_riser();