diff --git a/inputs/day04-example.txt b/inputs/day04-example.txt
new file mode 100644
index 0000000..669a51d
--- /dev/null
+++ b/inputs/day04-example.txt
@@ -0,0 +1,19 @@
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+
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+
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diff --git a/inputs/day04.txt b/inputs/day04.txt
new file mode 100644
index 0000000..c21b9b9
--- /dev/null
+++ b/inputs/day04.txt
@@ -0,0 +1,601 @@
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diff --git a/puzzles/TEMPLATE_test_dayXX.py b/puzzles/TEMPLATE_test_dayXX.py
index e6771c0..dc4ac8d 100644
--- a/puzzles/TEMPLATE_test_dayXX.py
+++ b/puzzles/TEMPLATE_test_dayXX.py
@@ -37,10 +37,10 @@ def test_example2(example_data2):
 
 
 @pytest.mark.skip(reason="Not implemented")
-def test_part1(day02_data):
-    assert aoc.part1(day02_data) == ...
+def test_part1(dayXX_data):
+    assert aoc.part1(dayXX_data) == ...
 
 
 @pytest.mark.skip(reason="Not implemented")
-def test_part2(day02_data):
-    assert aoc.part2(day02_data) == ...
+def test_part2(dayXX_data):
+    assert aoc.part2(dayXX_data) == ...
diff --git a/puzzles/day04.py b/puzzles/day04.py
new file mode 100644
index 0000000..2bf4571
--- /dev/null
+++ b/puzzles/day04.py
@@ -0,0 +1,102 @@
+"""
+Advent of Code 2021 - Day 04
+
+Run with:
+    python puzzles/day04.py inputs/day04.txt
+"""
+
+import pathlib
+import sys
+from typing import Dict, List, Tuple
+
+import numpy as np
+
+
+class Bingo:
+    boards = None
+    draws = None
+
+    def __init__(self, inputs: str) -> None:
+        inputs = inputs.split("\n\n")
+
+        # Convert all values to int
+        self.draws = list(map(int, inputs.pop(0).split(",")))
+        self.boards = np.array(
+            [
+                [list(map(int, value.split())) for value in line.split("\n")]
+                for line in inputs
+            ],
+            dtype=object,
+        )
+
+    def solve(self, squid_rules: bool = False) -> int:
+        game = self.boards.copy()
+        winning_scores = []
+        for draw in self._draw():
+            game[game == draw] = np.nan
+
+            for index, board in enumerate(game):
+                if self._is_solved(board):
+                    winning_scores.append(self._calculate_score(board, draw))
+
+                    try:
+                        game = np.delete(game, index, axis=0)
+                    except IndexError:  # I don't understand why this is needed
+                                        # Need to rework the whole class
+                                        # Wrong way to go about this
+                        pass
+
+            if len(winning_scores) == np.size(self.boards, axis=0):
+                break
+
+        index = -1 if squid_rules else 0
+        return winning_scores[index]
+
+    def _draw(self) -> int:
+        for draw in self.draws:
+            yield draw
+
+    @staticmethod
+    def _calculate_score(solved_board, last_draw: int) -> int:
+        board_score = np.nansum(solved_board)
+        return board_score * last_draw
+
+    @staticmethod
+    def _is_solved(board) -> bool:
+        # Solved if any row or column is 0
+        cols = np.nansum(board, axis=0)
+        rows = np.nansum(board, axis=1)
+        return (np.count_nonzero(cols) != cols.size or np.count_nonzero(rows) != rows.size)
+
+
+def part1(inputs: str) -> int:
+    game = Bingo(inputs)
+    return game.solve()
+
+
+def part2(inputs: str) -> int:
+    game = Bingo(inputs)
+    return game.solve(squid_rules=True)
+
+
+def solve(path: str) -> Tuple[int, int]:
+    """Solve the puzzle"""
+    inputs = pathlib.Path(path).read_text().strip()
+    part1_result = part1(inputs)
+    part2_result = part2(inputs)
+
+    return part1_result, part2_result
+
+
+def main() -> None:
+    for path in sys.argv[1:]:
+        print(f"Input File: {path}")
+
+        part1_result, part2_result = solve(path)
+
+        print(f"Part 1 Result: {part1_result}")
+        print(f"Part 2 Result: {part2_result}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/puzzles/test_day04.py b/puzzles/test_day04.py
new file mode 100644
index 0000000..64e10d9
--- /dev/null
+++ b/puzzles/test_day04.py
@@ -0,0 +1,32 @@
+import pathlib
+import pytest
+import day04 as aoc
+
+INPUTS_DIR = f"{pathlib.Path(__file__).parent.parent}/inputs"
+
+@pytest.fixture
+def example_data():
+    input_path = f"{INPUTS_DIR}/day04-example.txt"
+    return pathlib.Path(input_path).read_text().strip()
+
+
+@pytest.fixture
+def day04_data():
+    input_path = f"{INPUTS_DIR}/day04.txt"
+    return pathlib.Path(input_path).read_text().strip()
+
+
+def test_example1(example_data):
+    assert aoc.part1(example_data) == 4512
+
+
+def test_example2(example_data):
+    assert aoc.part2(example_data) == 1924
+
+
+def test_part1(day04_data):
+    assert aoc.part1(day04_data) == 25023
+
+
+def test_part2(day04_data):
+    assert aoc.part2(day04_data) == 2634