diff --git a/src/open.js b/src/open.js
index 095ba6c..e9bf5f2 100644
--- a/src/open.js
+++ b/src/open.js
@@ -16,10 +16,73 @@ function addStar() {
     let material = new THREE.MeshStandardMaterial({
         side: THREE.DoubleSide,
         color: 0x00ff00,
+        flatShading: true,
     });
+
     let star = new THREE.Mesh(geometry, material);
     star.receiveShadow = true;
     group.add(star);
+
+    let ringGeometry = generateStarRing(2, 3, 0.4);
+    let ring = new THREE.Mesh(ringGeometry, material);
+    group.add(ring);
+}
+
+/**
+ * Concatenate a series of Float32 arrays.
+ *
+ * @returns {Float32Array}
+ */
+function concatFloat32Array() {
+    let length = 0;
+    for (let cur of arguments) {
+        length += cur.length;
+    }
+
+    const buf = new Float32Array(length);
+    let offset = 0;
+    for (let cur of arguments) {
+        buf.set(cur, offset);
+        offset += cur.length;
+    }
+
+    return buf;
+}
+
+function generateStarRing(innerRadius, outerRadius, size) {
+    let vertexCandidates = [
+        starCoordinates(innerRadius + 0.5 * size, outerRadius + 0.5 * size, -0.5 * size),
+        starCoordinates(innerRadius + 0.5 * size, outerRadius + 0.5 * size, 0.5 * size),
+        starCoordinates(innerRadius - 0.5 * size, outerRadius - 0.5 * size, 0.5 * size),
+        starCoordinates(innerRadius - 0.5 * size, outerRadius - 0.5 * size, -0.5 * size),
+    ];
+    let vertices = concatFloat32Array(
+        vertexCandidates[0],
+        vertexCandidates[1],
+        vertexCandidates[2],
+        vertexCandidates[3],
+        vertexCandidates[1],
+        vertexCandidates[2],
+        vertexCandidates[0],
+        vertexCandidates[3],
+    );
+    console.log(vertices);
+
+    const faces = new Array(2 * STAR_POINTS * 3 * 4);
+    for (let i = 0; i < 4; ++i) {
+        const offset = 2 * 2 * STAR_POINTS * i;
+        for (let j = 0; j < 2 * STAR_POINTS; ++j) {
+            const nextRow = (j + 1) % (2 * STAR_POINTS);
+            faces.push(offset + j, offset + j + 2 * STAR_POINTS, offset + nextRow);
+            faces.push(offset + j + 2 * STAR_POINTS, offset + nextRow, offset + nextRow + 2 * STAR_POINTS);
+        }
+    }
+
+    let geometry = new THREE.BufferGeometry();
+    geometry.addAttribute('position', new THREE.BufferAttribute(vertices, 3));
+    geometry.setIndex(faces);
+
+    return geometry;
 }
 
 function startOpenAnimation() {