diff --git a/src/components/SampleLayout.tsx b/src/components/SampleLayout.tsx
index eca8a61a..6f93893e 100644
--- a/src/components/SampleLayout.tsx
+++ b/src/components/SampleLayout.tsx
@@ -136,6 +136,9 @@ const SampleLayout: React.FunctionComponent<
     };
     try {
       const canvas = canvasRef.current;
+      if (!canvas) {
+        throw new Error('The canvas is not available');
+      }
       const p = props.init({
         canvas,
         pageState,
@@ -190,7 +193,9 @@ const SampleLayout: React.FunctionComponent<
         <p>{props.description}</p>
         {error ? (
           <>
-            <p>Is WebGPU Enabled?</p>
+            <p>
+              Something went wrong. Do your browser and device support WebGPU?
+            </p>
             <p>{`${error}`}</p>
           </>
         ) : null}
@@ -253,3 +258,9 @@ export const makeSample: (
 ) => JSX.Element = (props) => {
   return <SampleLayout {...props} />;
 };
+
+export function assert(condition: unknown, msg?: string): asserts condition {
+  if (!condition) {
+    throw new Error(msg);
+  }
+}
diff --git a/src/pages/_app.tsx b/src/pages/_app.tsx
index 705fe378..86fbea7b 100644
--- a/src/pages/_app.tsx
+++ b/src/pages/_app.tsx
@@ -11,6 +11,10 @@ import { pages } from './samples/[slug]';
 
 const title = 'WebGPU Samples';
 
+type PageType = {
+  [key: string]: React.ComponentType & { render: { preload: () => void } };
+};
+
 const MainLayout: React.FunctionComponent<AppProps> = ({
   Component,
   pageProps,
@@ -71,7 +75,7 @@ const MainLayout: React.FunctionComponent<AppProps> = ({
                     key={slug}
                     className={className}
                     onMouseOver={() => {
-                      pages[slug].render.preload();
+                      (pages as PageType)[slug].render.preload();
                     }}
                   >
                     <Link
diff --git a/src/pages/samples/[slug].tsx b/src/pages/samples/[slug].tsx
index 1d5b4946..80b088aa 100644
--- a/src/pages/samples/[slug].tsx
+++ b/src/pages/samples/[slug].tsx
@@ -9,7 +9,11 @@ type Props = {
   slug: string;
 };
 
-export const pages = {
+type PageComponentType = {
+  [key: string]: React.ComponentType;
+};
+
+export const pages: PageComponentType = {
   helloTriangle: dynamic(() => import('../../sample/helloTriangle/main')),
   helloTriangleMSAA: dynamic(
     () => import('../../sample/helloTriangleMSAA/main')
@@ -59,9 +63,13 @@ export const getStaticPaths: GetStaticPaths<PathParams> = async () => {
 export const getStaticProps: GetStaticProps<Props, PathParams> = async ({
   params,
 }) => {
+  if (!params) {
+    return { notFound: true };
+  }
+
   return {
     props: {
-      ...params,
+      slug: params.slug,
     },
   };
 };
diff --git a/src/sample/animometer/main.ts b/src/sample/animometer/main.ts
index 5318c38e..8b6074af 100644
--- a/src/sample/animometer/main.ts
+++ b/src/sample/animometer/main.ts
@@ -1,9 +1,10 @@
-import { makeSample, SampleInit } from '../../components/SampleLayout';
+import { assert, makeSample, SampleInit } from '../../components/SampleLayout';
 
 import animometerWGSL from './animometer.wgsl';
 
 const init: SampleInit = async ({ canvas, pageState, gui }) => {
   const adapter = await navigator.gpu.requestAdapter();
+  assert(adapter, 'requestAdapter returned null');
   const device = await adapter.requestDevice();
 
   if (!pageState.active) return;
@@ -17,7 +18,11 @@ const init: SampleInit = async ({ canvas, pageState, gui }) => {
 
   const perfDisplay = document.createElement('pre');
   perfDisplayContainer.appendChild(perfDisplay);
-  canvas.parentNode.appendChild(perfDisplayContainer);
+  if (canvas.parentNode) {
+    canvas.parentNode.appendChild(perfDisplayContainer);
+  } else {
+    console.error('canvas.parentNode is null');
+  }
 
   const params = new URLSearchParams(window.location.search);
   const settings = {
@@ -272,16 +277,16 @@ const init: SampleInit = async ({ canvas, pageState, gui }) => {
       }
     }
 
-    let startTime = undefined;
+    let startTime: number | undefined = undefined;
     const uniformTime = new Float32Array([0]);
 
-    const renderPassDescriptor: GPURenderPassDescriptor = {
+    const renderPassDescriptor = {
       colorAttachments: [
         {
-          view: undefined, // Assigned later
+          view: undefined as any, // Assigned later
           clearValue: { r: 0.0, g: 0.0, b: 0.0, a: 1.0 },
-          loadOp: 'clear',
-          storeOp: 'store',
+          loadOp: 'clear' as const,
+          storeOp: 'store' as const,
         },
       ],
     };
@@ -292,7 +297,7 @@ const init: SampleInit = async ({ canvas, pageState, gui }) => {
     recordRenderPass(renderBundleEncoder);
     const renderBundle = renderBundleEncoder.finish();
 
-    return function doDraw(timestamp) {
+    return function doDraw(timestamp: number) {
       if (startTime === undefined) {
         startTime = timestamp;
       }
@@ -322,19 +327,23 @@ const init: SampleInit = async ({ canvas, pageState, gui }) => {
   const updateSettings = () => {
     doDraw = configure();
   };
-  gui
-    .add(settings, 'numTriangles', 0, 200000)
-    .step(1)
-    .onFinishChange(updateSettings);
-  gui.add(settings, 'renderBundles');
-  gui.add(settings, 'dynamicOffsets');
-
-  let previousFrameTimestamp = undefined;
-  let jsTimeAvg = undefined;
-  let frameTimeAvg = undefined;
+  if (gui === undefined) {
+    console.error('GUI not initialized');
+  } else {
+    gui
+      .add(settings, 'numTriangles', 0, 200000)
+      .step(1)
+      .onFinishChange(updateSettings);
+    gui.add(settings, 'renderBundles');
+    gui.add(settings, 'dynamicOffsets');
+  }
+
+  let previousFrameTimestamp: number | undefined = undefined;
+  let jsTimeAvg: number | undefined = undefined;
+  let frameTimeAvg: number | undefined = undefined;
   let updateDisplay = true;
 
-  function frame(timestamp) {
+  function frame(timestamp: number) {
     // Sample is no longer the active page.
     if (!pageState.active) return;
 
diff --git a/src/sample/computeBoids/main.ts b/src/sample/computeBoids/main.ts
index e6505bb1..ae8db740 100644
--- a/src/sample/computeBoids/main.ts
+++ b/src/sample/computeBoids/main.ts
@@ -1,10 +1,11 @@
-import { makeSample, SampleInit } from '../../components/SampleLayout';
+import { assert, makeSample, SampleInit } from '../../components/SampleLayout';
 
 import spriteWGSL from './sprite.wgsl';
 import updateSpritesWGSL from './updateSprites.wgsl';
 
 const init: SampleInit = async ({ canvas, pageState, gui }) => {
   const adapter = await navigator.gpu.requestAdapter();
+  assert(adapter, 'requestAdapter returned null');
   const device = await adapter.requestDevice();
 
   if (!pageState.active) return;
@@ -85,13 +86,13 @@ const init: SampleInit = async ({ canvas, pageState, gui }) => {
     },
   });
 
-  const renderPassDescriptor: GPURenderPassDescriptor = {
+  const renderPassDescriptor = {
     colorAttachments: [
       {
-        view: undefined, // Assigned later
+        view: undefined as any, // Assigned later
         clearValue: { r: 0.0, g: 0.0, b: 0.0, a: 1.0 },
-        loadOp: 'clear',
-        storeOp: 'store',
+        loadOp: 'clear' as const,
+        storeOp: 'store' as const,
       },
     ],
   };
@@ -144,7 +145,12 @@ const init: SampleInit = async ({ canvas, pageState, gui }) => {
 
   updateSimParams();
   Object.keys(simParams).forEach((k) => {
-    gui.add(simParams, k).onFinishChange(updateSimParams);
+    const key = k as keyof typeof simParams;
+    if (gui === undefined) {
+      console.error('GUI not initialized');
+    } else {
+      gui.add(simParams, key).onFinishChange(updateSimParams);
+    }
   });
 
   const numParticles = 1500;
diff --git a/src/sample/resizeCanvas/main.ts b/src/sample/resizeCanvas/main.ts
index 58eea106..51be312f 100644
--- a/src/sample/resizeCanvas/main.ts
+++ b/src/sample/resizeCanvas/main.ts
@@ -1,4 +1,4 @@
-import { makeSample, SampleInit } from '../../components/SampleLayout';
+import { assert, makeSample, SampleInit } from '../../components/SampleLayout';
 
 import triangleVertWGSL from '../../shaders/triangle.vert.wgsl';
 import redFragWGSL from '../../shaders/red.frag.wgsl';
@@ -7,6 +7,7 @@ import styles from './animatedCanvasSize.module.css';
 
 const init: SampleInit = async ({ canvas, pageState }) => {
   const adapter = await navigator.gpu.requestAdapter();
+  assert(adapter, 'requestAdapter returned null');
   const device = await adapter.requestDevice();
 
   if (!pageState.active) return;
diff --git a/src/types.d.ts b/src/types.d.ts
index b12b0998..d32080f6 100644
--- a/src/types.d.ts
+++ b/src/types.d.ts
@@ -25,3 +25,6 @@ declare module '*.wgsl' {
   const shader: string;
   export default shader;
 }
+
+declare module 'stats-js';
+declare module 'stanford-dragon/4';