add the background layer

Shared/World.cs

@@ -102,6 +102,8 @@ namespace SemiColinGames {
     public World(string json) {
       JObject root = JObject.Parse(json);
 
+      List<Tile> decorationTiles = new List<Tile>();
+      List<Tile> backgroundTiles = new List<Tile>();
       foreach (JToken layer in root.SelectToken("layers").Children()) {
         string layerName = layer.SelectToken("name").Value<string>();
         if (layerName == "entities") {
@@ -110,13 +112,18 @@ namespace SemiColinGames {
           continue;
         }
         List<Tile> tileList = ParseLayer(layer);
-        // TODO: add background layer
         if (layerName == "obstacles") {
           tiles = tileList.ToArray();
         } else if (layerName == "decorations") {
-          decorations = tileList.ToArray();
+          decorationTiles = tileList;
+        } else if (layerName == "background") {
+          backgroundTiles = tileList;
         }
       }
+      // The background tiles are added before the rest of the decorations, so that they're drawn
+      // in the back.
+      backgroundTiles.AddRange(decorationTiles);
+      decorations = backgroundTiles.ToArray();
       Debug.WriteLine("world size: {0}x{1}", gridWidth, gridHeight);
 
       // Because we added tiles from left to right, the CollisionTargets are sorted by x-position.