config.json in trackler-2.2.1.11

- old
+ new

@@ -1,8 +1,9 @@
 {
   "language": "C#",
   "active": true,
+  "blurb": "C# is a modern, object-oriented language with lots of great features, such as type-inference and async/await. The official documentation is very extensive and well-written.",
   "exercises": [
     {
       "uuid": "6c88f46b-5acb-4fae-a6ec-b48ae3f8168f",
       "slug": "hello-world",
       "core": true,
@@ -44,10 +45,21 @@
         "Arrays",
         "Transforming"
       ]
     },
     {
+      "uuid": "57f02d0e-7b75-473b-892d-26a7d980c4ce",
+      "slug": "two-fer",
+      "core": true,
+      "unlocked_by": "null",
+      "difficulty": 1,
+      "topics": [
+        "Strings",
+        "Optional values"
+      ]
+    },
+    {
       "uuid": "29ae7f8e-a009-4175-9350-a8c684c89730",
       "slug": "raindrops",
       "core": true,
       "unlocked_by": null,
       "difficulty": 2,
@@ -89,10 +101,24 @@
         "Lists",
         "Sorting"
       ]
     },
     {
+      "uuid": "c4efbf8a-8e76-4700-807d-830a4938f4d0",
+      "slug": "collatz-conjecture",
+      "core": false,
+      "unlocked_by": "sum-of-multiples",
+      "difficulty": 2,
+      "topics": [
+        "Control-flow (loops)",
+        "Control-flow (conditionals)",
+        "Integers",
+        "Algorithms",
+        "Mathematics"
+      ]
+    },
+    {
       "uuid": "b7458404-2534-4ed8-8350-7060fa4b5786",
       "slug": "kindergarten-garden",
       "core": true,
       "unlocked_by": null,
       "difficulty": 3,
@@ -854,9 +880,20 @@
       "unlocked_by": "markdown",
       "difficulty": 5,
       "topics": [
         "Algorithms",
         "Transforming"
+      ]
+    },
+    {
+      "uuid": "bae1f3a4-b63d-4efd-921a-133b3d5e379c",
+      "slug": "spiral-matrix",
+      "core": false,
+      "unlocked_by": "matrix",
+      "difficulty": 5,
+      "topics": [
+        "Algorithms",
+        "Matrices"
       ]
     },
     {
       "uuid": "d9359f25-dc94-496c-adc3-57fe541857fe",
       "slug": "tournament",