diff --git a/2021/d6.py b/2021/d6.py
new file mode 100644
index 0000000..6207b94
--- /dev/null
+++ b/2021/d6.py
@@ -0,0 +1,32 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+
+data = get_data(__file__).strip()
+xs = ints(data)
+
+for _ in range(80):
+    for i in range(len(xs)):
+        if xs[i] == 0:
+            xs[i] = 6
+            xs.append(8)
+        else:
+            xs[i] -= 1
+
+print(len(xs))
+
+xs = ints(data)
+fish = defaultdict(int)
+for x in xs:
+    fish[x] += 1
+
+for _ in range(256):
+    new_fish = defaultdict(int)
+    new_fish[8] = fish[0]
+    new_fish[6] = fish[0]
+    for i in range(1, 9):
+        new_fish[i - 1] += fish[i]
+    fish = new_fish
+
+r = sum(fish.values())
+print(r)
diff --git a/README.md b/README.md
index bede23a..4c26602 100644
--- a/README.md
+++ b/README.md
@@ -177,7 +177,8 @@ Solutions and utility script for Advent of Code challenges in Python.
 - Day 3: 23:46   (How long can I take when I try to take long?)
 - Day 4: 22:18   (No way. Such stupid bugs.)
 - Day 5: 13:30   (Decent, but obviously too slow.)
-- Day 6:
+- Day 6: 16:33   (Right idea quickly but then struggled to implement.)
+- Day 7: 
 
 ## AoC 2022