Take a rough swing at phone support

index.html

@@ -10,6 +10,7 @@
     <meta name="og:image" content="https://c.eev.ee/lexys-labyrinth/og-preview.png">
     <meta name="og:title" content="Lexy's Labyrinth">
     <meta name="og:description" content="A (work in progress) reimplementation of Chip's Challenge 1 and 2, using entirely free assets.">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
 </head>
 <body data-mode="splash">
     <header id="header-main">
@@ -116,10 +117,10 @@
         </div>
         <div class="controls">
             <div class="play-controls">
-                <button class="control-pause" type="button">Pause (p)</button>
+                <button class="control-pause" type="button">Pause <span class="keyhint">(p)</span></button>
                 <button class="control-restart" type="button">Restart</button>
                 <button class="control-undo" type="button">Undo</button>
-                <button class="control-rewind" type="button">Rewind (z)</button>
+                <button class="control-rewind" type="button">Rewind <span class="keyhint">(z)</span></button>
             </div>
             <div class="demo-controls">
                 <button class="demo-play" type="button">View replay</button>