diff --git a/answer_cache.json b/answer_cache.json
index 91252e8..bae588c 100644
--- a/answer_cache.json
+++ b/answer_cache.json
@@ -83,5 +83,15 @@
             "wrong": [],
             "correct": 37453
         }
+    },
+    "9": {
+        "1": {
+            "wrong": [],
+            "correct": 412959
+        },
+        "2": {
+            "wrong": [],
+            "correct": 3333662986
+        }
     }
 }
\ No newline at end of file
diff --git a/day09.py b/day09.py
new file mode 100644
index 0000000..0df28b7
--- /dev/null
+++ b/day09.py
@@ -0,0 +1,77 @@
+from collections import defaultdict
+
+from tools.aoc import AOCDay
+from typing import Any
+
+
+class Marble:
+    number: int
+    left: 'Marble'
+    right: 'Marble'
+
+    def __init__(self, number: int):
+        self.number = number
+
+
+def play(players: int, marbles: int):
+    current = Marble(0)
+    current.left = current
+    current.right = current
+
+    scores = defaultdict(int)
+
+    next_num = 1
+    player = 0
+
+    while next_num <= marbles:
+        this_marble = Marble(next_num)
+        if next_num % 23 == 0:
+            scores[player] = scores[player] + this_marble.number
+            for _ in range(7):
+                current = current.left
+            scores[player] = scores[player] + current.number
+            current.left.right = current.right
+            current.right.left = current.left
+            current = current.right
+        else:
+            current = current.right
+            this_marble.left = current
+            this_marble.right = current.right
+            current.right.left = this_marble
+            current.right = this_marble
+            current = this_marble
+
+        player = (player + 1) % players
+        next_num += 1
+
+    return max(scores.values())
+
+
+class Day(AOCDay):
+    inputs = [
+        [
+            (8317, "input9_test1"),
+            (146373, "input9_test2"),
+            (412959, "input9"),
+        ],
+        [
+            (3333662986, "input9"),
+        ]
+    ]
+
+    def parse_input(self) -> (int, int):
+        parts = self.getInput().split(" ")
+        return int(parts[0]), int(parts[6])
+
+    def part1(self) -> Any:
+        return play(*self.parse_input())
+
+    def part2(self) -> Any:
+        players, marbles = self.parse_input()
+        marbles *= 100
+        return play(players, marbles)
+
+
+if __name__ == '__main__':
+    day = Day(2018, 9)
+    day.run(verbose=True)
diff --git a/inputs/input9 b/inputs/input9
new file mode 100644
index 0000000..52d49b9
--- /dev/null
+++ b/inputs/input9
@@ -0,0 +1 @@
+435 players; last marble is worth 71184 points
diff --git a/inputs/input9_test1 b/inputs/input9_test1
new file mode 100644
index 0000000..f94a71a
--- /dev/null
+++ b/inputs/input9_test1
@@ -0,0 +1 @@
+10 players; last marble is worth 1618 points
\ No newline at end of file
diff --git a/inputs/input9_test2 b/inputs/input9_test2
new file mode 100644
index 0000000..266e075
--- /dev/null
+++ b/inputs/input9_test2
@@ -0,0 +1 @@
+13 players; last marble is worth 7999 points
\ No newline at end of file