diff --git a/2021/README.md b/2021/README.md
index 937e179..6d6285b 100644
--- a/2021/README.md
+++ b/2021/README.md
@@ -14,7 +14,7 @@
 
 |  S  |  M  |  T  |  W  |  T  |  F  |  S  |
 | :-: | :-: | :-: | :-: | :-: | :-: | :-: |
-|     |     |     |  1  |  2  |  3  |  4  |
+|     |     |     | [1] |  2  |  3  |  4  |
 |  5  |  6  |  7  |  8  |  9  | 10  | 11  |
 | 12  | 13  | 14  | 15  | 16  | 17  | 18  |
 | 19  | 20  | 21  | 22  | 23  | 24  | 25  |
@@ -38,3 +38,5 @@ A behaviour for a solution to a puzzle. Must define a `solve/2` callback.
 Case template defining an `assert_solution/2` helper.
 
 <!-- links -->
+
+[1]: ./lib/advent_of_code/day01.ex
diff --git a/2021/lib/advent_of_code/day01.ex b/2021/lib/advent_of_code/day01.ex
new file mode 100644
index 0000000..ec57e31
--- /dev/null
+++ b/2021/lib/advent_of_code/day01.ex
@@ -0,0 +1,37 @@
+defmodule AdventOfCode.Day01 do
+  @moduledoc """
+  Day 1
+  """
+end
+
+defmodule AdventOfCode.Day01.Part1 do
+  @moduledoc """
+  Day 1, Part 1
+  """
+
+  alias AdventOfCode.PuzzleSolver
+  use PuzzleSolver
+
+  import AdventOfCode.Day01, warn: false
+
+  @impl PuzzleSolver
+  def solve(_input_stream) do
+    :ok |> to_string()
+  end
+end
+
+defmodule AdventOfCode.Day01.Part2 do
+  @moduledoc """
+  Day 1, Part 2
+  """
+
+  alias AdventOfCode.PuzzleSolver
+  use PuzzleSolver
+
+  import AdventOfCode.Day01, warn: false
+
+  @impl PuzzleSolver
+  def solve(_input_stream) do
+    :ok |> to_string()
+  end
+end
\ No newline at end of file
diff --git a/2021/test/advent_of_code/day01/part_1_test.exs b/2021/test/advent_of_code/day01/part_1_test.exs
new file mode 100644
index 0000000..f9a9557
--- /dev/null
+++ b/2021/test/advent_of_code/day01/part_1_test.exs
@@ -0,0 +1,11 @@
+defmodule AdventOfCode.Day01.Part1Test do
+  use AdventOfCode.PuzzleCase, module: AdventOfCode.Day01.Part1
+
+  test "returns :ok" do
+    input = ~S"""
+    input
+    """
+
+    assert_solution(input, "ok")
+  end
+end
\ No newline at end of file
diff --git a/2021/test/advent_of_code/day01/part_2_test.exs b/2021/test/advent_of_code/day01/part_2_test.exs
new file mode 100644
index 0000000..13711f3
--- /dev/null
+++ b/2021/test/advent_of_code/day01/part_2_test.exs
@@ -0,0 +1,11 @@
+defmodule AdventOfCode.Day01.Part2Test do
+  use AdventOfCode.PuzzleCase, module: AdventOfCode.Day01.Part2
+
+  test "returns :ok" do
+    input = ~S"""
+    input
+    """
+
+    assert_solution(input, "ok")
+  end
+end
\ No newline at end of file