Implement viewport size override debug setting

index.html

@@ -147,7 +147,7 @@
             <div class="input"></div>
             <div class="-options">
                 <p> Viewport size:
-                    <select id="player-debug-viewport" disabled>
+                    <select id="player-debug-viewport">
                         <option value="default" selected>Level default (9 or 10)</option>
                         <option value="12">12 × 12</option>
                         <option value="16">16 × 16</option>