bare-think-off/claude-opus-5 / tier-2-l-bracket

```openscad
// L-bracket with countersunk holes for M4 screws
// Inner corner at origin; horizontal flange extends +Y, vertical flange extends +Z

// ---------- Parameters ----------
width      = 50;   // X: common width of both flanges
h_depth    = 40;   // Y: horizontal flange depth
v_height   = 40;   // Z: vertical flange height
thick      = 3;    // plate thickness

hole_d     = 4.5;  // through hole diameter (M4 clearance)
cs_d       = 8;    // countersink face diameter
cs_depth   = 2;    // countersink depth

edge_off   = 10;   // distance from flange outer edge to hole center
x_off      = 15;   // holes symmetric about X center, +/- x_off

$fn = 64;

// ---------- Countersunk hole cutter ----------
// Cut along -Z direction from the outer surface (z = 0 is the outer face).
// Countersink cone opens upward (toward the tool/bolt head side).
module countersunk_hole(plate_t = thick) {
    eps = 0.01;
    union() {
        // through hole
        translate([0, 0, -plate_t - eps])
            cylinder(h = plate_t + 2 * eps, d = hole_d);
        // countersink cone (cs_d at outer face -> hole_d at cs_depth)
        translate([0, 0, -cs_depth])
            cylinder(h = cs_depth, d1 = hole_d, d2 = cs_d);
        // small clearance above the outer face
        translate([0, 0, -eps])
            cylinder(h = cs_depth, d = cs_d);
    }
}

// ---------- Bracket ----------
module l_bracket() {
    difference() {
        union() {
            // horizontal flange: X 0..width, Y 0..h_depth, Z -thick..0
            translate([0, 0, -thick])
                cube([width, h_depth, thick]);
            // vertical flange: X 0..width, Y -thick..0, Z 0..v_height
            translate([0, -thick, 0])
                cube([width, thick, v_height]);
            // fill inner corner block
            translate([0, -thick, -thick])
                cube([width, thick, thick]);
        }

        // --- holes in horizontal flange (countersink on bottom, z = -thick) ---
        for (dx = [-x_off, x_off])
            translate([width / 2 + dx, h_depth - edge_off, -thick])
                rotate([180, 0, 0])
                    countersunk_hole(thick);

        // --- holes in vertical flange (countersink on front, y = -thick) ---
        for (dx = [-x_off, x_off])
            translate([width / 2 + dx, -thick, v_height - edge_off])
                rotate([-90, 0, 0])
                    countersunk_hole(thick);
    }
}

l_bracket();
```