diff --git a/advent-of-typescript/2023/day_05.ts b/advent-of-typescript/2023/day_05.ts
new file mode 100644
index 0000000..896addb
--- /dev/null
+++ b/advent-of-typescript/2023/day_05.ts
@@ -0,0 +1,48 @@
+import { Equal, Expect } from "type-testing";
+
+/* -----------------------------------------------------------------------------------------------
+ * Code here
+ * -----------------------------------------------------------------------------------------------*/
+
+type SantasList<T extends readonly Object[], U extends readonly Object[]> = [
+  ...T,
+  ...U,
+];
+
+/* -----------------------------------------------------------------------------------------------
+ * Do not edit below this line
+ * -----------------------------------------------------------------------------------------------*/
+
+const bads = ["tommy", "trash"] as const;
+const goods = ["bash", "tru"] as const;
+
+type test_0_actual = SantasList<typeof bads, typeof goods>;
+//   ^?
+type test_0_expected = ["tommy", "trash", "bash", "tru"];
+type test_0 = Expect<Equal<test_0_actual, test_0_expected>>;
+
+type test_1_actual = SantasList<[], []>;
+//   ^?
+type test_1_expected = [];
+type test_1 = Expect<Equal<test_1_actual, test_1_expected>>;
+
+type test_2_actual = SantasList<[], ["trash"]>;
+//   ^?
+type test_2_expected = ["trash"];
+type test_2 = Expect<Equal<test_2_actual, test_2_expected>>;
+
+type test_3_actual = SantasList<["john"], ["ashley", "elliot", "ziltoid"]>;
+//   ^?
+type test_3_expected = ["john", "ashley", "elliot", "ziltoid"];
+type test_3 = Expect<Equal<test_3_actual, test_3_expected>>;
+
+type test_4_actual = SantasList<
+  ["1", 2, "3"],
+  [false, boolean, "4", ["nested"]]
+>;
+//   ^?
+type test_4_expected = ["1", 2, "3", false, boolean, "4", ["nested"]];
+type test_4 = Expect<Equal<test_4_actual, test_4_expected>>;
+
+// @ts-expect-error
+type error_0 = SantasList<null, undefined>;
diff --git a/advent-of-typescript/2023/day_06.ts b/advent-of-typescript/2023/day_06.ts
new file mode 100644
index 0000000..c24f0bd
--- /dev/null
+++ b/advent-of-typescript/2023/day_06.ts
@@ -0,0 +1,35 @@
+import { Equal, Expect } from "type-testing";
+
+/* -----------------------------------------------------------------------------------------------
+ * Code here
+ * -----------------------------------------------------------------------------------------------*/
+
+type FilterChildrenBy<T, U> = Exclude<T, U>;
+
+/* -----------------------------------------------------------------------------------------------
+ * Do not edit below this line
+ * -----------------------------------------------------------------------------------------------*/
+
+type test_0_actual = FilterChildrenBy<
+  //   ^?
+  "nice" | "nice" | "nice",
+  "naughty"
+>;
+type test_0_expected = "nice";
+type test_0 = Expect<Equal<test_0_expected, test_0_actual>>;
+
+type test_1_actual = FilterChildrenBy<
+  //   ^?
+  "nice" | "naughty" | "naughty",
+  "naughty"
+>;
+type test_1_expected = "nice";
+type test_1 = Expect<Equal<test_1_expected, test_1_actual>>;
+
+type test_2_actual = FilterChildrenBy<
+  //   ^?
+  string | number | (() => void),
+  Function
+>;
+type test_2_expected = string | number;
+type test_2 = Expect<Equal<test_2_expected, test_2_actual>>;
diff --git a/package.json b/package.json
index c4d6f1c..732c469 100644
--- a/package.json
+++ b/package.json
@@ -28,7 +28,7 @@
   "lint-staged": {
     "*.ts": [
       "oxlint --fix .",
-      "prettier . --cache"
+      "prettier ."
     ]
   },
   "commitlint": {