diff --git a/11/11.py b/11/11.py
new file mode 100755
index 0000000..ec06d9f
--- /dev/null
+++ b/11/11.py
@@ -0,0 +1,95 @@
+#!/usr/bin/env python
+# 2021 - Advent Of Code - 11
+
+GRID_SIZE = 10
+
+
+def parse_file(file):
+    with open(file) as f:
+        columns = []
+        for line in f.readlines():
+            columns.append([int(c) for c in line.strip()])
+
+        return columns
+
+
+def print_grid(grid):
+    for y in range(GRID_SIZE):
+        for x in range(GRID_SIZE):
+            print(grid[y][x], end='')
+        print()
+    print()
+
+
+def check_flash(grid, f):
+    for y in range(GRID_SIZE):
+        for x in range(GRID_SIZE):
+            if grid[y][x] > 9:
+                f = flash(grid, x, y, f)
+    return f
+
+
+def flash(grid, x, y, f):
+    grid[y][x] = 0
+    f += 1
+    if y > 0:   # upper neighbours
+        if x > 0:
+            if grid[y-1][x-1] != 0:  # 1
+                grid[y-1][x-1] += 1
+                if grid[y-1][x-1] > 9:
+                    f = flash(grid, x-1, y-1, f)
+        if grid[y-1][x] != 0:  # 2
+            grid[y-1][x] += 1
+            if grid[y-1][x] > 9:
+                f = flash(grid, x, y-1, f)
+
+        if x < GRID_SIZE-1:
+            if grid[y-1][x+1] != 0:  # 3
+                grid[y-1][x+1] += 1
+                if grid[y-1][x+1] > 9:
+                    f = flash(grid, x+1, y-1, f)
+
+    if x > 0:  # middle neighbours
+        if grid[y][x-1] != 0:  # 4
+            grid[y][x-1] += 1
+            if grid[y][x-1] > 9:
+                f = flash(grid, x-1, y, f)
+    if x < GRID_SIZE - 1:  # 6
+        if grid[y][x+1] != 0:
+            grid[y][x+1] += 1
+            if grid[y][x+1] > 9:
+                f = flash(grid, x+1, y, f)
+
+    if y < GRID_SIZE-1:  # down neighbours
+        if x > 0:
+            if grid[y+1][x-1] != 0:  # 7
+                grid[y+1][x-1] += 1
+                if grid[y+1][x-1] > 9:
+                    f = flash(grid, x-1, y+1, f)
+        if grid[y+1][x] != 0:    # 8
+            grid[y+1][x] += 1
+            if grid[y + 1][x] > 9:
+                f = flash(grid, x, y+1, f)
+        if x < GRID_SIZE-1:
+            if grid[y+1][x+1] != 0:      # 9
+                grid[y+1][x+1] += 1
+                if grid[y+1][x+1] > 9:
+                    f = flash(grid, x+1, y+1, f)
+    return f
+
+
+octopus_map = parse_file('input.txt')
+# octopus_map = parse_file('input_example.txt')
+print_grid(octopus_map)
+
+nbflash = 0
+for step in range(100):
+    # increase all energy levels
+    for mapy in range(GRID_SIZE):
+        for mapx in range(GRID_SIZE):
+            octopus_map[mapy][mapx] += 1
+
+    nbflash = check_flash(octopus_map, nbflash)
+    print_grid(octopus_map)
+
+print(f'number of flash: {nbflash}')
diff --git a/11/input.txt b/11/input.txt
new file mode 100644
index 0000000..497e9f0
--- /dev/null
+++ b/11/input.txt
@@ -0,0 +1,10 @@
+8258741254
+3335286211
+8468661311
+6164578353
+2138414553
+1785385447
+3441133751
+3586862837
+7568272878
+6833643144
diff --git a/11/input_example.txt b/11/input_example.txt
new file mode 100644
index 0000000..03743f6
--- /dev/null
+++ b/11/input_example.txt
@@ -0,0 +1,10 @@
+5483143223
+2745854711
+5264556173
+6141336146
+6357385478
+4167524645
+2176841721
+6882881134
+4846848554
+5283751526