diff --git a/2021/11/README.md b/2021/11/README.md
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+++ b/2021/11/README.md
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+# 11
+
+Description
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>1749</li>
+    <li>285</li>
+  </ol>
+</details>
diff --git a/2021/11/python/main.py b/2021/11/python/main.py
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+++ b/2021/11/python/main.py
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+#!/usr/bin/env python
+
+from os.path import dirname, join
+
+# Day 11
+
+# Common
+
+
+def read_input(filename):
+    data = join(dirname(__file__), '..', filename)
+    with open(data) as f:
+        return f.read().strip()
+
+
+test = read_input('test.txt')
+data = read_input('input.txt')
+
+
+def bold(text: str) -> str:
+    return f'\033[1m{text}\033[0m'
+
+
+def red(text: str) -> str:
+    return f'\033[31m{text}\033[0m'
+
+
+class OctoGrid:
+
+    def __init__(self, grid: list[list[int]]) -> None:
+        self.grid = grid
+        self.flashed = set()
+        self.x = len(grid[0])
+        self.y = len(grid)
+
+    def _flash(self, x: int, y: int):
+        if (x, y) in self.flashed:
+            return False
+        self.flashed.add((x, y))
+        # print(f"Flash at {y}, {x}")
+        for dx in range(-1, 2):
+            for dy in range(-1, 2):
+                # if dx == dy == 0:
+                #     continue
+                target_x = x + dx
+                target_y = y + dy
+                if 0 <= target_x < self.x and 0 <= target_y < self.y:
+                    self.grid[target_y][target_x] += 1
+        return True
+
+    def _check(self):
+        for y in range(self.y):
+            for x in range(self.x):
+                if self.grid[y][x] > 9:
+                    if self._flash(x, y):
+                        return True
+        return False
+
+    def _step(self):
+        self.flashed.clear()
+
+        # Increase all by one
+        for y in range(self.y):
+            for x in range(self.x):
+                self.grid[y][x] += 1
+
+        while self._check():
+            pass
+
+        for y in range(self.y):
+            for x in range(self.x):
+                if self.grid[y][x] > 9:
+                    self.grid[y][x] = 0
+
+        return len(self.flashed)
+
+    def count_flashes(self, steps):
+        total = 0
+        for _ in range(steps):
+            total += self._step()
+        return total
+
+    def first_simultaneous(self):
+        step = 0
+        while True:
+            step += 1
+            if self._step() == self.y * self.x:
+                return step
+
+    def __str__(self) -> str:
+        def f(x):
+            s = str(x).ljust(3, ' ')
+            if x > 9:
+                s = bold(red(s))
+            return s
+        s = ''
+        for y in range(self.y):
+            s += ''.join(f(x) for x in self.grid[y]) + '\n'
+        return s
+
+    @staticmethod
+    def parse(data):
+        grid = [
+            list(map(int, line))
+            for line
+            in data.splitlines()
+        ]
+        return OctoGrid(grid)
+
+
+        # 1
+print('1.')
+
+grid = OctoGrid.parse(test)
+print(grid.count_flashes(100))
+grid = OctoGrid.parse(test)
+print(grid.first_simultaneous())
+
+# 2
+print('\n2.')
+
+grid = OctoGrid.parse(data)
+print(grid.count_flashes(100))
+grid = OctoGrid.parse(data)
+print(grid.first_simultaneous())