diff --git a/react-slideshow/src/App.js b/react-slideshow/src/App.js
index c29cf84..8f596a1 100644
--- a/react-slideshow/src/App.js
+++ b/react-slideshow/src/App.js
@@ -5,9 +5,22 @@ import {
   Route,
   useParams
 } from "react-router-dom";
-
+import Random from './rand';
 import './App.css';
 
+let CONFIG;
+if (process.env.NODE_ENV === 'production') {
+  CONFIG = {
+    sleepTimeSeconds: 5 * 60,
+    showUI: false,
+  }
+} else {
+  CONFIG = {
+    sleepTimeSeconds: 10,
+    showUI: true,
+  }
+}
+
 const IMAGE_CHUNK = 256;
 const roundup = (v, mod) => {
   let r = v % mod;
@@ -18,6 +31,20 @@ const roundup = (v, mod) => {
   }
 };
 
+/**
+ * Shuffles array in place. ES6 version
+ * From https://stackoverflow.com/questions/6274339/how-can-i-shuffle-an-array
+ * @param {Array} a items An array containing the items.
+ */
+function shuffle(a) {
+  let rng = new Random(new Date().getDay());
+    for (let i = a.length - 1; i > 0; i--) {
+        const j = Math.floor(rng.nextFloat() * (i + 1));
+        [a[i], a[j]] = [a[j], a[i]];
+    }
+    return a;
+}
+
 class Album extends React.Component {
   constructor(props) {
     super(props);
@@ -25,6 +52,7 @@ class Album extends React.Component {
       error: null,
       mediaItems: null,
       idx: 0,
+      showUI: props.showUI,
     };
   }
   componentDidMount() {
@@ -52,18 +80,44 @@ class Album extends React.Component {
       h = roundup(h, IMAGE_CHUNK);
       w = (h/ratio).toFixed();
     }
+    console.log(`Window size ${window.innerWidth}x${window.innerHeight} with a devicePixelRatio of ${window.devicePixelRatio} for a total size of ${w}x${h}`);
 
     //let w = roundup(window.innerWidth*window.devicePixelRatio, IMAGE_CHUNK);
     //let h = roundup(window.innerHeight*window.devicePixelRatio, IMAGE_CHUNK);
-    let {idx, error, mediaItems} = this.state;
+    let {idx, error, mediaItems, showUI} = this.state;
     if (error !== null) {
       return <h2>Error: {JSON.stringify(error)}</h2>;
     } else if (mediaItems !== null) {
-      let numImages = mediaItems.length;
+      let landscapes = mediaItems.filter((mi) => {
+        let md = mi.mediaMetadata;
+        let ratio = md.width/md.height;
+        return ratio > 1;
+      });
+
+      let portraits = mediaItems.filter((mi) => {
+        let md = mi.mediaMetadata;
+        let ratio = md.width/md.height;
+        return ratio <= 1;
+      });
+
+      console.log(`${landscapes.length} landscape photos`);
+      console.log(`${portraits.length} portraits photos`);
+      let photos;
+      if (ratio > 1) {
+        console.log('display in landscape mode');
+        photos = landscapes;
+      } else {
+        console.log('display in portrait mode');
+        photos = portraits;
+      }
+      photos = shuffle(photos);
+
+      let numImages = photos.length;
       let nextIdx = (idx+1)%numImages;
       let prevIdx = (numImages+idx-1)%numImages;
-      let image = mediaItems[idx];
-      let nextImage = mediaItems[nextIdx];
+      let image = photos[idx];
+      let nextImage = photos[nextIdx];
+      let prevImage = photos[prevIdx];
       let style = {
         height: '100%',
         width: '100%',
@@ -74,26 +128,44 @@ class Album extends React.Component {
         backgroundSize: 'cover',
       };
       let prefetchStyle = {
-        // display: 'none'
         position: 'absolute',
-        right: 0,
-        bottom: 0,
         width: '25%',
         height: '25%',
+        bottom: 0,
       };
-      console.log(`window.devicePixelRatio ${window.devicePixelRatio}`);
-      return <div style={style} onClick={(e)=>{
-        e.stopPropagation();
-        this.setState({idx: nextIdx})
-      }}>
-        <img
-          style={prefetchStyle}
+      let leftPrefetchStyle = {
+        left: 0,
+        ...prefetchStyle
+      };
+      let rightPrefetchStyle = {
+        right: 0,
+        ...prefetchStyle
+      };
+      let ui;
+      if (showUI) {
+        ui = <div>
+          <img
+          style={leftPrefetchStyle}
           onClick={(e)=>{
             e.stopPropagation();
             this.setState({idx: prevIdx})
           }}
+          src={`/api/image/${prevImage.id}?w=${w}&h=${h}`} alt="prefetch prev" />
+          <img
+          style={rightPrefetchStyle}
+          onClick={(e)=>{
+            e.stopPropagation();
+            this.setState({idx: nextIdx})
+          }}
           src={`/api/image/${nextImage.id}?w=${w}&h=${h}`} alt="prefetch next" />
         </div>;
+      }
+      return <div style={style} onClick={(e)=>{
+        e.stopPropagation();
+        this.setState({showUI: !showUI})
+      }}>
+        { ui }
+        </div>;
     } else {
       return <h2>Loading...</h2>;
     }
@@ -141,14 +213,15 @@ class AlbumIndex extends React.Component {
   }
 }
 
-const AlbumRoute = () => {
+const AlbumRoute = ({showUI}) => {
   // We can use the `useParams` hook here to access
   // the dynamic pieces of the URL.
   let { albumId } = useParams();
-  return <Album album={albumId} />;
+  return <Album album={albumId} showUI={showUI} />;
 }
 
 const App = () => {
+  let {showUI} = CONFIG;
   return <Router>
       <Switch>
         <Route exact path="/">
@@ -157,7 +230,7 @@ const App = () => {
           </div>
         </Route>
         <Route exact path="/:albumId">
-          <AlbumRoute />
+          <AlbumRoute showUI={showUI} />
         </Route>
       </Switch>
     </Router>
diff --git a/react-slideshow/src/rand.js b/react-slideshow/src/rand.js
new file mode 100644
index 0000000..2d2344d
--- /dev/null
+++ b/react-slideshow/src/rand.js
@@ -0,0 +1,30 @@
+// From https://gist.github.com/blixt/f17b47c62508be59987b
+/**
+ * Creates a pseudo-random value generator. The seed must be an integer.
+ *
+ * Uses an optimized version of the Park-Miller PRNG.
+ * http://www.firstpr.com.au/dsp/rand31/
+ */
+function Random(seed) {
+  console.log(`Seeding prng with ${seed}`);
+  this._seed = seed % 2147483647;
+  if (this._seed <= 0) this._seed += 2147483646;
+}
+
+/**
+ * Returns a pseudo-random value between 1 and 2^32 - 2.
+ */
+Random.prototype.next = function () {
+  return this._seed = this._seed * 16807 % 2147483647;
+};
+
+
+/**
+ * Returns a pseudo-random floating point number in range [0, 1).
+ */
+Random.prototype.nextFloat = function (opt_minOrMax, opt_max) {
+  // We know that result of next() will be 1 to 2147483646 (inclusive).
+  return (this.next() - 1) / 2147483646;
+};
+
+export default Random;