allow for background-only ("no tile")

includes/script.js

@@ -123,6 +123,13 @@ $(document).ready(function() {
         // get tiles
         bitsyData.tiles = {};
 
+        // tile 0 (background colour only) is implicit in bitsy rather than being stored in the game data
+        // so, make our own version
+        bitsyData.tiles[0] = {
+            name: 0, 
+            bitmap: _.chunk(_.split(_.repeat(0, 64), ''), 8)
+        };
+
         var tiles = input.match(/TIL (.*)\n([01]{8}\n){8}/g);
 
         if (tiles.length > 0) {