Kris makes polygon close automatically

src/animation/Flash.ts

@@ -0,0 +1,42 @@
+import { Animation } from "./Animation.js";
+import * as THREE from "three";
+
+export default class Flash extends Animation {
+    constructor(
+        object: THREE.Object3D,
+        fadeOut: boolean = false,
+        startTime: number,
+        endTime: number,
+    ) {
+        super(
+            (_elapsedTime) => {
+                let alpha;
+                if (!fadeOut) {
+                    if (_elapsedTime < startTime) {
+                        alpha = 0;
+                    } else if (_elapsedTime === startTime) {
+                        alpha = 1;
+                    } else {
+                        alpha = 1;
+                    }
+                } else {
+                    const midpoint = (startTime + endTime) / 2;
+                    if (_elapsedTime < startTime) {
+                        alpha = 0;
+                    } else if (_elapsedTime < midpoint) {
+                        const t0 = (_elapsedTime - startTime) / (midpoint - startTime);
+                        alpha = t0;
+                    } else if (_elapsedTime < endTime) {
+                        const t1 = (_elapsedTime - midpoint) / (endTime - midpoint);
+                        alpha = 1 - t1;
+                    } else {
+                        alpha = 0;
+                    }
+                }
+
+                object.setOpacity(alpha);
+            },
+            { object, reveal: true },
+        );
+    }
+}

src/animation/index.ts

@@ -10,4 +10,5 @@ export { default as SetOpacity } from "./SetOpacity.js";
 export { default as FadeOut } from "./FadeOut.js";
 export { default as Wait } from "./Wait.js";
 export { default as Emphasize } from "./Emphasize.js";
-export { default as Shake } from "./Shake.js";
+export { default as Shake } from "./Shake.js";
+export { default as Flash } from "./Flash.js";

src/geometry/Polygon.ts

@@ -14,6 +14,11 @@ export type PolygonAttributes = {
 
 export default class Polygon extends Shape {
   constructor(points: Array<THREE.Vector3>, config: Style = {}) {
+    // Ensure the polygon is closed by adding the first point to the end
+    if (points.length > 0 && !points[0].equals(points[points.length - 1])) {
+      points.push(points[0]);
+    }
+
     super(points, { ...Polygon.defaultConfig(), ...config });
     this.curveEndIndices = [];
     for (let i = 0; i < points.length - 1; i++) {