diff --git a/.formatter.exs b/.formatter.exs
new file mode 100644
index 0000000..d2cda26
--- /dev/null
+++ b/.formatter.exs
@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..58881af
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,26 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+yt_ext-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/
diff --git a/lib/yt_ext.ex b/lib/yt_ext.ex
new file mode 100644
index 0000000..072f923
--- /dev/null
+++ b/lib/yt_ext.ex
@@ -0,0 +1,18 @@
+defmodule YtExt do
+  @moduledoc """
+  Documentation for `YtExt`.
+  """
+
+  @doc """
+  Hello world.
+
+  ## Examples
+
+      iex> YtExt.hello()
+      :world
+
+  """
+  def hello do
+    :world
+  end
+end
diff --git a/lib/yt_ext/application.ex b/lib/yt_ext/application.ex
new file mode 100644
index 0000000..f1283fc
--- /dev/null
+++ b/lib/yt_ext/application.ex
@@ -0,0 +1,20 @@
+defmodule YtExt.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    children = [
+      # Starts a worker by calling: YtExt.Worker.start_link(arg)
+      # {YtExt.Worker, arg}
+    ]
+
+    # See https://hexdocs.pm/elixir/Supervisor.html
+    # for other strategies and supported options
+    opts = [strategy: :one_for_one, name: YtExt.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+end
diff --git a/lib/yt_ext/youtube_id.ex b/lib/yt_ext/youtube_id.ex
new file mode 100644
index 0000000..3007422
--- /dev/null
+++ b/lib/yt_ext/youtube_id.ex
@@ -0,0 +1,20 @@
+defmodule YouTubeID do
+  @youtube_chars "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
+  @base length(String.graphemes(@youtube_chars))
+
+  def to_integer(<<video_id::binary-size(11)>>) do
+    video_id
+    |> String.graphemes()
+    |> Enum.reverse()
+    |> Enum.with_index()
+    |> Enum.reduce(0, fn {char, index}, acc ->
+      char_value = contains_at(@youtube_chars, char)
+      acc + char_value * trunc(:math.pow(@base, index))
+    end)
+  end
+
+  defp contains_at(string, char) do
+    String.split(string, "", trim: true)
+    |> Enum.find_index(&(&1 == char))
+  end
+end
diff --git a/mix.exs b/mix.exs
new file mode 100644
index 0000000..a28533f
--- /dev/null
+++ b/mix.exs
@@ -0,0 +1,29 @@
+defmodule YtExt.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :yt_ext,
+      version: "0.1.0",
+      elixir: "~> 1.17",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger],
+      mod: {YtExt.Application, []}
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end
diff --git a/test/test_helper.exs b/test/test_helper.exs
new file mode 100644
index 0000000..869559e
--- /dev/null
+++ b/test/test_helper.exs
@@ -0,0 +1 @@
+ExUnit.start()
diff --git a/test/yt_ext_test.exs b/test/yt_ext_test.exs
new file mode 100644
index 0000000..56e9995
--- /dev/null
+++ b/test/yt_ext_test.exs
@@ -0,0 +1,8 @@
+defmodule YtExtTest do
+  use ExUnit.Case
+  doctest YtExt
+
+  test "greets the world" do
+    assert YtExt.hello() == :world
+  end
+end