diff --git a/src/__tests__/day_9_test.ts b/src/__tests__/day_9_test.ts
index 503888c..a6ed60e 100644
--- a/src/__tests__/day_9_test.ts
+++ b/src/__tests__/day_9_test.ts
@@ -1,5 +1,9 @@
 import { assertEquals } from "@std/assert";
-import { get_largest_area, read_tile_floor } from "../exercises/day_9.ts";
+import {
+  get_largest_area,
+  get_largest_green_area,
+  read_tile_floor,
+} from "../exercises/day_9.ts";
 
 Deno.test("Day 9 - A", async () => {
   const floor = await read_tile_floor(
@@ -8,3 +12,11 @@ Deno.test("Day 9 - A", async () => {
   const result = get_largest_area(floor);
   assertEquals(result, 50);
 });
+
+Deno.test("Day 9 - B", async () => {
+  const floor = await read_tile_floor(
+    "src/exercises/assets/day_9_test_input.txt",
+  );
+  const result = get_largest_green_area(floor);
+  assertEquals(result, 24);
+});
diff --git a/src/exercises/day_9.ts b/src/exercises/day_9.ts
index 37720ad..5e4579e 100644
--- a/src/exercises/day_9.ts
+++ b/src/exercises/day_9.ts
@@ -14,6 +14,10 @@ export default async function MovieTheater() {
     "src/exercises/assets/day_9_input.txt",
   );
   console.log(">> Largest red-tile area: ", get_largest_area(floor));
+  console.log(
+    ">> Largest red-green-tile area: ",
+    get_largest_green_area(floor),
+  );
 }
 
 export function get_largest_area(floor: Floor): number {
@@ -43,6 +47,87 @@ export function get_largest_area(floor: Floor): number {
   return largest_area;
 }
 
+export function get_largest_green_area(floor: Floor): number {
+  let largest_area: number = 0;
+  floor.red_tiles.forEach((tile, tile_i) => {
+    for (
+      let inner_i = tile_i + 1;
+      inner_i < floor.red_tiles.length;
+      inner_i++
+    ) {
+      const inner_tile = floor.red_tiles[inner_i];
+      if (is_area_red_green(floor, tile, inner_tile)) {
+        const height = calc_distance({ x: tile.x, y: tile.y }, {
+          x: tile.x,
+          y: inner_tile.y,
+        });
+        const width = calc_distance({ x: tile.x, y: tile.y }, {
+          x: inner_tile.x,
+          y: tile.y,
+        });
+        const new_area = (width + 1) * (height + 1); // NOTE: +1 to count  also the outer tiles
+        if (new_area > largest_area) {
+          largest_area = new_area;
+        }
+      }
+    }
+  });
+
+  return largest_area;
+}
+
+function is_area_red_green(
+  floor: Floor,
+  a: Coordinate,
+  b: Coordinate,
+): boolean {
+  const max_x = Math.max(a.x, b.x);
+  const max_y = Math.max(a.y, b.y);
+  const min_x = Math.min(a.x, b.x);
+  const min_y = Math.min(a.y, b.y);
+
+  const tl_corner: Coordinate = { x: min_x, y: min_y };
+  const tr_corner: Coordinate = { x: max_x, y: min_y };
+  const bl_corner: Coordinate = { x: min_x, y: max_y };
+  const br_corner: Coordinate = { x: max_x, y: max_y };
+
+  // Find valid closers
+  // Every corner needs to be surrounded
+
+  // NOTE: I don't think this will be enough
+  // Maybe not cover corners and cover verticals
+  // l
+  const l_cover =
+    floor.red_tiles.some((tile) =>
+      tile.x <= tl_corner.x && tile.y <= tl_corner.y
+    ) && floor.red_tiles.some((tile) =>
+      tile.x <= bl_corner.x && tile.y >= bl_corner.y
+    );
+  // r
+  const r_cover =
+    floor.red_tiles.some((tile) =>
+      tile.x >= tr_corner.x && tile.y <= tr_corner.y
+    ) && floor.red_tiles.some((tile) =>
+      tile.x >= br_corner.x && tile.y >= br_corner.y
+    );
+  // b
+  const b_cover =
+    floor.red_tiles.some((tile) =>
+      tile.x <= bl_corner.x && tile.y >= bl_corner.y
+    ) && floor.red_tiles.some((tile) =>
+      tile.x >= br_corner.x && tile.y >= br_corner.y
+    );
+  // t
+  const t_cover =
+    floor.red_tiles.some((tile) =>
+      tile.x <= tr_corner.x && tile.y <= tr_corner.y
+    ) && floor.red_tiles.some((tile) =>
+      tile.x >= tl_corner.x && tile.y <= tl_corner.y
+    );
+
+  return l_cover && r_cover && b_cover && t_cover;
+}
+
 function calc_distance(a: Coordinate, b: Coordinate): number {
   return Math.sqrt(Math.pow(a.x - b.x, 2) + Math.pow(a.y - b.y, 2));
 }