diff --git a/2021-python/solutions/day_11.py b/2021-python/solutions/day_11.py
new file mode 100644
index 0000000..1ed2d50
--- /dev/null
+++ b/2021-python/solutions/day_11.py
@@ -0,0 +1,66 @@
+from solutions import BaseSolution
+from collections import deque
+
+
+class Solution(BaseSolution):
+    input_file = "11.txt"
+
+    def __str__(self):
+        return "Day 11: Dumbo Octopus"
+
+    def parse_input(self, data):
+        return [list(map(int, d)) for d in data.split()]
+
+    def solve(self, puzzle_input, steps=100):
+        flashes = self._tick(puzzle_input, steps, exit_on_bright=False)
+        return flashes
+
+    def solve_again(self, puzzle_input, steps=100):
+        brightest = self._tick(puzzle_input, steps, exit_on_bright=True)
+        return brightest
+
+    def _debug(self, d):
+        print("\n")
+        for r in d:
+            print("".join(map(str, r)))
+
+    def _tick(self, matrix, steps, exit_on_bright=False):
+        my = len(matrix)
+        mx = len(matrix[0])
+        offsets = [(-1, -1), (-1, 0), (-1, 1), (0, -1), (0, 1), (1, -1), (1, 0), (1, 1)]
+        f = 0
+        # self._debug(matrix)
+        counter = 0
+        while 1:
+            if not exit_on_bright and not counter < steps:
+                break
+            if exit_on_bright:
+                if sum(sum(c for c in r) for r in matrix) == 0:
+                    return counter
+            matrix = [[(c + 1) % 10 for c in r] for r in matrix]
+            flash = deque()
+            for y, r in enumerate(matrix):
+                for x, v in enumerate(r):
+                    if v == 0:
+                        flash.append((y, x))
+            while flash:
+                f += 1
+                y, x = flash.popleft()
+                for ay, ax in offsets:
+                    oy, ox = y + ay, x + ax
+                    if oy < 0 or ox < 0 or oy >= my or ox >= mx:
+                        continue
+                    v = matrix[oy][ox]
+                    if v == 0:
+                        continue
+                    matrix[oy][ox] = (v + 1) % 10
+                    if v == 9:
+                        flash.append((oy, ox))
+            # self._debug(matrix)
+            counter += 1
+        return f
+
+
+if __name__ == "__main__":
+    solution = Solution()
+    solution.show_results()
diff --git a/2021-python/tests/test_day_11.py b/2021-python/tests/test_day_11.py
new file mode 100644
index 0000000..6c816e2
--- /dev/null
+++ b/2021-python/tests/test_day_11.py
@@ -0,0 +1,47 @@
+import unittest
+
+from solutions.day_11 import Solution
+
+
+class Day11TestCase(unittest.TestCase):
+    def setUp(self):
+        self.solution = Solution()
+        self.puzzle_input = self.solution.parse_input(
+            """
+        5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526
+        """
+        )
+
+    def test_parse_puzzle_input(self):
+        data = """
+        1234
+        5678
+        """
+        assert self.solution.parse_input(data) == [[1, 2, 3, 4], [5, 6, 7, 8]]
+
+    def test_solve_first_part(self):
+        data = """
+        11111
+19991
+19191
+19991
+11111
+        """
+        assert self.solution.solve(self.solution.parse_input(data), 2) == 9
+        assert self.solution.solve(self.puzzle_input) == 1656
+
+    def test_solve_second_part(self):
+        assert self.solution.solve_again(self.puzzle_input) == 195
+
+
+if __name__ == "__main__":
+    unittest.main()