diff --git a/advent-of-typescript/2023/day_18.ts b/advent-of-typescript/2023/day_18.ts
new file mode 100644
index 0000000..afedf15
--- /dev/null
+++ b/advent-of-typescript/2023/day_18.ts
@@ -0,0 +1,140 @@
+import { Equal, Expect } from "type-testing";
+
+import { Increment } from "@/utils/type-helpers";
+
+/* -----------------------------------------------------------------------------------------------
+ * Code here
+ * -----------------------------------------------------------------------------------------------*/
+
+type Count<T, E, C extends any[] = []> = T extends [infer S, ...infer R]
+  ? S extends E // if the current element is the element we're counting
+    ? Count<R, E, Increment<C>> // increment the count and recurse
+    : Count<R, E, C> // otherwise, recurse for the rest of the array without incrementing
+  : C["length"]; // if we've reached the end of the array, return the count
+
+/* -----------------------------------------------------------------------------------------------
+ * Do not edit below this line
+ * -----------------------------------------------------------------------------------------------*/
+
+type ToySack = [
+  "🎸",
+  "🎧",
+  "👟",
+  "👟",
+  "💻",
+  "🪀",
+  "🧩",
+  "🎮",
+  "🎨",
+  "🕹️",
+  "📱",
+  "🧩",
+  "🧸",
+  "🎧",
+  "👟",
+  "🚲",
+  "📚",
+  "⌚",
+  "🎨",
+  "👟",
+  "🎸",
+  "🧸",
+  "👟",
+  "🎸",
+  "📱",
+  "🎧",
+  "🎮",
+  "🎒",
+  "📱",
+  "🧩",
+  "🧩",
+  "🚲",
+  "🕹️",
+  "🧵",
+  "📱",
+  "🕹️",
+  "🕰️",
+  "🧢",
+  "🕹️",
+  "👟",
+  "🧸",
+  "📚",
+  "🧁",
+  "🧩",
+  "🎸",
+  "🎮",
+  "🧁",
+  "📚",
+  "💻",
+  "⌚",
+  "🛹",
+  "🧁",
+  "🧣",
+  "🪁",
+  "🎸",
+  "🧸",
+  "🧸",
+  "🧸",
+  "🧩",
+  "🪁",
+  "🏎️",
+  "🏎️",
+  "🧁",
+  "📚",
+  "🧸",
+  "🕶️",
+  "💻",
+  "⌚",
+  "⌚",
+  "🕶️",
+  "🎧",
+  "🎧",
+  "🎧",
+  "💻",
+  "👟",
+  "🎸",
+  "💻",
+  "🪐",
+  "📚",
+  "🎨",
+  "📱",
+  "🎧",
+  "📱",
+  "🎸",
+  "🏎️",
+  "👟",
+  "🚲",
+  "📱",
+  "🚲",
+  "🎸",
+];
+
+type test_0_actual = Count<ToySack, "👟">;
+//   ^?
+type test_0_expected = 8;
+type test_0 = Expect<Equal<test_0_expected, test_0_actual>>;
+
+type test_1_actual = Count<ToySack, "🧦">;
+//   ^?
+type test_1_expected = 0;
+type test_1 = Expect<Equal<test_1_expected, test_1_actual>>;
+
+type test_2_actual = Count<ToySack, "🧩">;
+//   ^?
+type test_2_expected = 6;
+type test_2 = Expect<Equal<test_2_expected, test_2_actual>>;
+
+type test_3_actual = Count<ToySack, "🛹">;
+//   ^?
+type test_3_expected = 1;
+type test_3 = Expect<Equal<test_3_expected, test_3_actual>>;
+
+type test_4_actual = Count<ToySack, "🏎️">;
+//   ^?
+type test_4_expected = 3;
+type test_4 = Expect<Equal<test_4_expected, test_4_actual>>;
+
+type test_5_actual = Count<ToySack, "📚">;
+//   ^?
+type test_5_expected = 5;
+type test_5 = Expect<Equal<test_5_expected, test_5_actual>>;