Portrait mode and one-handed touch controls (drag/flick/tap)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

index.html

@@ -9,6 +9,7 @@
   canvas { image-rendering: pixelated; width: min(96vw, calc(96vh * 16 / 9)); aspect-ratio: 16/9; touch-action: none; }
   #hint { position: fixed; bottom: 8px; width: 100%; text-align: center;
           font: 12px monospace; color: #6b7688; }
+  @media (pointer: coarse) { #hint { display: none; } }
 </style>
 </head>
 <body>