added portals (closes #4) and first level of puzzle mode

levels/puzzle1.json

@@ -0,0 +1,21 @@
+{
+	"dimensions": [15, 10],
+	"walls": [
+		[5, 0], [5, 1], [5, 2], [5, 3], [5, 4], [5, 5], [5, 6], [5, 7], [5, 8], [5, 9],
+		[10, 0], [10, 1], [10, 2], [10, 3], [10, 4], [10, 5], [10, 6], [10, 7], [10, 8], [10, 9]
+	],
+	"food": [
+		[4, 5],
+		[8, 7],
+		[14, 9]
+	],
+	"snake": [
+		[0, 0]
+	],
+	"portals": {
+		"a": [4, 9],
+		"b": [6, 0],
+		"c": [9, 9],
+		"d": [11, 0]
+	}
+}