diff --git a/challenges/2021/11.js b/challenges/2021/11.js
new file mode 100644
index 0000000..bae5430
--- /dev/null
+++ b/challenges/2021/11.js
@@ -0,0 +1,63 @@
+// Part 1
+const solvePuzzle1 = (input) => {
+  input = parseInput(input);
+  let flashed = 0;
+
+  for (let i = 0; i < 100; i++) {
+    const flashedCoords = new Set();
+    for (let y = 0; y < input.length; y++) {
+      for (let x = 0; x < input[0].length; x++) {
+        flashed += increment(y, x, input, flashedCoords);
+      }
+    }
+  }
+
+  return flashed;
+};
+
+// Part 2
+const solvePuzzle2 = (input) => {
+  input = parseInput(input);
+  const [width, height] = [input.length, input[0].length];
+  const boardSize = width * height;
+  let [step, flashedCoords] = [0, new Set()];
+
+  while (flashedCoords.size < boardSize) {
+    flashedCoords = new Set();
+    step += 1;
+    for (let y = 0; y < width; y++) {
+      for (let x = 0; x < height; x++) {
+        increment(y, x, input, flashedCoords);
+      }
+    }
+  }
+
+  return step;
+};
+
+const increment = (y, x, board, flashedCoords) => {
+  let flashed = 0;
+  if (board[y] === undefined || board[y][x] === undefined || flashedCoords.has(`${y},${x}`)) return flashed;
+
+  if (board[y][x] >= 0 && board[y][x] < 9) {
+    board[y][x]++;
+  } else {
+    flashedCoords.add(`${y},${x}`);
+    flashed = 1;
+    board[y][x] = 0;
+    forEachSurrounding(y, x, (h, w) => (flashed += increment(h, w, board, flashedCoords)));
+  }
+  return flashed;
+};
+
+const parseInput = (input) => input.split("\n").map((l) => l.split("").map((x) => Number(x)));
+const forEachSurrounding = (y, x, callback) => {
+  for (let h = y - 1; h <= y + 1; h++) {
+    for (let w = x - 1; w <= x + 1; w++) {
+      if (h !== y || w !== x) callback(h, w);
+    }
+  }
+};
+
+require(__dirname + "/../../utils/test.js").test(__filename, __dirname, solvePuzzle1);
+require(__dirname + "/../../utils/test.js").test(__filename, __dirname, solvePuzzle2);
diff --git a/challenges/2021/inputs/11.txt b/challenges/2021/inputs/11.txt
new file mode 100644
index 0000000..6df6231
--- /dev/null
+++ b/challenges/2021/inputs/11.txt
@@ -0,0 +1,10 @@
+5212166716
+1567322581
+2268461548
+3481561744
+6248342248
+6526667368
+5627335775
+8124511754
+4614137683
+4724561156
\ No newline at end of file