diff --git a/advent-of-code/2023/elixir/day_07/.formatter.exs b/advent-of-code/2023/day_07/.formatter.exs
similarity index 100%
rename from advent-of-code/2023/elixir/day_07/.formatter.exs
rename to advent-of-code/2023/day_07/.formatter.exs
diff --git a/advent-of-code/2023/elixir/day_07/.gitignore b/advent-of-code/2023/day_07/.gitignore
similarity index 100%
rename from advent-of-code/2023/elixir/day_07/.gitignore
rename to advent-of-code/2023/day_07/.gitignore
diff --git a/advent-of-code/2023/elixir/day_07/README.md b/advent-of-code/2023/day_07/README.md
similarity index 84%
rename from advent-of-code/2023/elixir/day_07/README.md
rename to advent-of-code/2023/day_07/README.md
index 45a690f..5284015 100644
--- a/advent-of-code/2023/elixir/day_07/README.md
+++ b/advent-of-code/2023/day_07/README.md
@@ -1,4 +1,8 @@
-# Day 7: Camel Cards
+# Advent of Code 2023 day 7 solution in Elixir
+
+## Camel Cards
+
+[Task page](https://adventofcode.com/2023/day/7)
 
 Your all-expenses-paid trip turns out to be a one-way, five-minute ride in an airship.
 (At least it's a cool airship!) It drops you off at the edge of a vast desert and descends back to Island Island.
@@ -19,7 +23,8 @@ but the machines have broken down because Desert Island recently stopped receivi
 
 You've already assumed it'll be your job to figure out why the parts stopped when she asks if you can help. You agree automatically.
 
-Because the journey will take a few days, she offers to teach you the game of Camel Cards. Camel Cards is sort of similar to poker except it's designed to be easier to play while riding a camel.
+Because the journey will take a few days, she offers to teach you the game of Camel Cards.
+Camel Cards is sort of similar to poker except it's designed to be easier to play while riding a camel.
 
 In Camel Cards, you get a list of hands, and your goal is to order them based on the strength of each hand.
 A hand consists of five cards labeled one of `A`, `K`, `Q`, `J`, `T`, `9`, `8`, `7`, `6`, `5`, `4`, `3`, or `2`.
@@ -27,13 +32,14 @@ The relative strength of each card follows this order, where `A` is the highest
 
 Every hand is exactly one type. From strongest to weakest, they are:
 
-- Five of a kind, where all five cards have the same label: AAAAA
-- Four of a kind, where four cards have the same label and one card has a different label: AA8AA
-- Full house, where three cards have the same label, and the remaining two cards share a different label: 23332
-- Three of a kind, where three cards have the same label, and the remaining two cards are each different from any other card in the hand: TTT98
-- Two pair, where two cards share one label, two other cards share a second label, and the remaining card has a third label: 23432
-- One pair, where two cards share one label, and the other three cards have a different label from the pair and each other: A23A4
-- High card, where all cards' labels are distinct: 23456
+- Five of a kind, where all five cards have the same label: `AAAAA`
+- Four of a kind, where four cards have the same label and one card has a different label: `AA8AA`
+- Full house, where three cards have the same label, and the remaining two cards share a different label: `23332`
+- Three of a kind, where three cards have the same label, and the remaining two cards are each different
+  from any other card in the hand: `TTT98`
+- Two pair, where two cards share one label, two other cards share a second label, and the remaining card has a third label: `23432`
+- One pair, where two cards share one label, and the other three cards have a different label from the pair and each other: `A23A4`
+- High card, where all cards' labels are distinct: `23456`
 
 Hands are primarily ordered based on type; for example, every full house is stronger than any three of a kind.
 
@@ -65,13 +71,16 @@ Because there are five hands in this example, the strongest hand will have rank
 So, the first step is to put the hands in order of strength:
 
 - `32T3K` is the only one pair and the other hands are all a stronger type, so it gets rank 1.
-- `KK677` and `KTJJT` are both two pair. Their first cards both have the same label, but the second card of `KK677` is stronger (K vs T), so `KTJJT` gets rank 2 and `KK677` gets rank 3.
+- `KK677` and `KTJJT` are both two pair. Their first cards both have the same label,
+  but the second card of `KK677` is stronger (K vs T), so `KTJJT` gets rank 2 and `KK677` gets rank 3.
 - `T55J5` and `QQQJA` are both three of a kind. `QQQJA` has a stronger first card, so it gets rank 5 and `T55J5` gets rank 4.
 
-Now, you can determine the total winnings of this set of hands by adding up the result of multiplying each hand's bid with its rank (765 * 1 + 220 * 2 + 28 * 3 + 684 * 4 + 483 * 5). So the total winnings in this example are 6440.
+Now, you can determine the total winnings of this set of hands by adding up the result of multiplying each hand's bid with
+its rank (765 * 1 + 220 * 2 + 28 * 3 + 684 * 4 + 483 * 5). So the total winnings in this example are 6440.
 
 Find the rank of every hand in your set. What are the total winnings?
 
+
 ## Part Two
 
 To make things a little more interesting, the Elf introduces one additional rule.
diff --git a/advent-of-code/2023/elixir/day_07/test/input.txt b/advent-of-code/2023/day_07/input.txt
similarity index 100%
rename from advent-of-code/2023/elixir/day_07/test/input.txt
rename to advent-of-code/2023/day_07/input.txt
diff --git a/advent-of-code/2023/elixir/day_07/lib/solution.ex b/advent-of-code/2023/day_07/lib/cards.ex
similarity index 72%
rename from advent-of-code/2023/elixir/day_07/lib/solution.ex
rename to advent-of-code/2023/day_07/lib/cards.ex
index 799f6f4..aae4c69 100644
--- a/advent-of-code/2023/elixir/day_07/lib/solution.ex
+++ b/advent-of-code/2023/day_07/lib/cards.ex
@@ -1,12 +1,5 @@
-defmodule Solution do
-  @spec get_total_winnings(String.t()) :: integer()
-  def get_total_winnings(filename, with_jokers \\ false) do
-    hands =
-      filename
-      |> File.stream!()
-      |> Enum.map(&parse_line/1)
-      |> Map.new()
-
+defmodule Cards do
+  def get_total_winnings(hands, with_jokers \\ false) do
     sorted_cards =
       hands
       |> Map.keys()
@@ -17,15 +10,6 @@ defmodule Solution do
     |> Enum.reduce(0, fn {el, idx}, acc -> acc + idx * hands[el] end)
   end
 
-  defp parse_line(line) do
-    [hand, bid] =
-      line
-      |> String.trim()
-      |> String.split(" ")
-
-    {hand, String.to_integer(bid)}
-  end
-
   # Map a hand to a list that may be used for sorting.
   defp get_sorting_order(hand, with_jokers) do
     # Map cards to corresponding power,
@@ -44,13 +28,13 @@ defmodule Solution do
 
   ## Examples
 
-    iex> Solution.get_card_power("J")
+    iex> Cards.get_card_power("J")
     11
 
-    iex> Solution.get_card_power("J", true)
+    iex> Cards.get_card_power("J", true)
     1
 
-    iex> Solution.get_card_power("5")
+    iex> Cards.get_card_power("5")
     5
   """
   def get_card_power(card, with_jokers \\ false) do
@@ -80,25 +64,25 @@ defmodule Solution do
 
   ## Examples
 
-      iex> Solution.get_rank("AAAAA")
+      iex> Cards.get_rank("AAAAA")
       7
 
-      iex> Solution.get_rank("AA8AA")
+      iex> Cards.get_rank("AA8AA")
       6
 
-      iex> Solution.get_rank("23332")
+      iex> Cards.get_rank("23332")
       5
 
-      iex> Solution.get_rank("TTT98")
+      iex> Cards.get_rank("TTT98")
       4
 
-      iex> Solution.get_rank("23432")
+      iex> Cards.get_rank("23432")
       3
 
-      iex> Solution.get_rank("A23A4")
+      iex> Cards.get_rank("A23A4")
       2
 
-      iex> Solution.get_rank("23456")
+      iex> Cards.get_rank("23456")
       1
   """
   def get_rank(hand, with_jokers \\ false) do
@@ -134,13 +118,13 @@ defmodule Solution do
 
   ## Examples
 
-      iex> Solution.replace_joker("T55J5")
+      iex> Cards.replace_joker("T55J5")
       "T5555"
 
-      iex> Solution.replace_joker("KTJJT")
+      iex> Cards.replace_joker("KTJJT")
       "KTTTT"
 
-      iex> Solution.replace_joker("JJJJJ")
+      iex> Cards.replace_joker("JJJJJ")
       "AAAAA"
   """
   def replace_joker(hand) do
diff --git a/advent-of-code/2023/day_07/lib/parser.ex b/advent-of-code/2023/day_07/lib/parser.ex
new file mode 100644
index 0000000..22460ef
--- /dev/null
+++ b/advent-of-code/2023/day_07/lib/parser.ex
@@ -0,0 +1,17 @@
+defmodule Parser do
+  def parse_file(filename) do
+    filename
+    |> File.stream!()
+    |> Stream.map(&parse_line/1)
+    |> Map.new()
+  end
+
+  defp parse_line(line) do
+    [hand, bid] =
+      line
+      |> String.trim()
+      |> String.split(" ")
+
+    {hand, String.to_integer(bid)}
+  end
+end
diff --git a/advent-of-code/2023/day_07/lib/task.ex b/advent-of-code/2023/day_07/lib/task.ex
new file mode 100644
index 0000000..50d7498
--- /dev/null
+++ b/advent-of-code/2023/day_07/lib/task.ex
@@ -0,0 +1,10 @@
+defmodule Mix.Tasks.Solve do
+  use Mix.Task
+
+  def run(_) do
+    hands = Parser.parse_file("input.txt")
+
+    IO.puts("Part 1: #{Cards.get_total_winnings(hands)}")
+    IO.puts("Part 2: #{Cards.get_total_winnings(hands, true)}")
+  end
+end
diff --git a/advent-of-code/2023/elixir/day_07/mix.exs b/advent-of-code/2023/day_07/mix.exs
similarity index 55%
rename from advent-of-code/2023/elixir/day_07/mix.exs
rename to advent-of-code/2023/day_07/mix.exs
index 351fecd..0d88219 100644
--- a/advent-of-code/2023/elixir/day_07/mix.exs
+++ b/advent-of-code/2023/day_07/mix.exs
@@ -11,18 +11,13 @@ defmodule Day07.MixProject do
     ]
   end
 
-  # Run "mix help compile.app" to learn about applications.
   def application do
     [
       extra_applications: [:logger]
     ]
   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/advent-of-code/2023/day_07/test/cards_test.exs b/advent-of-code/2023/day_07/test/cards_test.exs
new file mode 100644
index 0000000..01e7d74
--- /dev/null
+++ b/advent-of-code/2023/day_07/test/cards_test.exs
@@ -0,0 +1,14 @@
+defmodule CardsTest do
+  use ExUnit.Case
+  doctest Cards
+
+  test "example 1" do
+    hands = Parser.parse_file("test/example.txt")
+    assert Cards.get_total_winnings(hands) == 6440
+  end
+
+  test "example 2" do
+    hands = Parser.parse_file("test/example.txt")
+    assert Cards.get_total_winnings(hands, true) == 5905
+  end
+end
diff --git a/advent-of-code/2023/elixir/day_07/test/example.txt b/advent-of-code/2023/day_07/test/example.txt
similarity index 100%
rename from advent-of-code/2023/elixir/day_07/test/example.txt
rename to advent-of-code/2023/day_07/test/example.txt
diff --git a/advent-of-code/2023/elixir/day_07/test/test_helper.exs b/advent-of-code/2023/day_07/test/test_helper.exs
similarity index 100%
rename from advent-of-code/2023/elixir/day_07/test/test_helper.exs
rename to advent-of-code/2023/day_07/test/test_helper.exs
diff --git a/advent-of-code/2023/elixir/day_08/.formatter.exs b/advent-of-code/2023/day_08/.formatter.exs
similarity index 100%
rename from advent-of-code/2023/elixir/day_08/.formatter.exs
rename to advent-of-code/2023/day_08/.formatter.exs
diff --git a/advent-of-code/2023/elixir/day_08/.gitignore b/advent-of-code/2023/day_08/.gitignore
similarity index 100%
rename from advent-of-code/2023/elixir/day_08/.gitignore
rename to advent-of-code/2023/day_08/.gitignore
diff --git a/advent-of-code/2023/elixir/day_08/README.md b/advent-of-code/2023/day_08/README.md
similarity index 85%
rename from advent-of-code/2023/elixir/day_08/README.md
rename to advent-of-code/2023/day_08/README.md
index 0129694..fa2f60f 100644
--- a/advent-of-code/2023/elixir/day_08/README.md
+++ b/advent-of-code/2023/day_08/README.md
@@ -1,4 +1,8 @@
-# Day 8
+# Advent of Code 2023 day 8 solution in Elixir
+
+## Haunted Wasteland
+
+[Task page](https://adventofcode.com/2023/day/8)
 
 You're still riding a camel across Desert Island when you spot a sandstorm quickly approaching.
 When you turn to warn the Elf, she disappears before your eyes! To be fair, she had just finished warning you about ghosts a few minutes ago.
@@ -45,6 +49,7 @@ ZZZ = (ZZZ, ZZZ)
 
 Starting at AAA, follow the left/right instructions. How many steps are required to reach ZZZ?
 
+
 ## Part Two
 
 The sandstorm is upon you and you aren't any closer to escaping the wasteland.
@@ -79,15 +84,13 @@ Repeat this process until all of the nodes you're currently on end with Z.
 (If only some of the nodes you're on end with Z, they act like any other node and you continue as normal.)
 In this example, you would proceed as follows:
 
-```
-    Step 0: You are at 11A and 22A.
-    Step 1: You choose all of the left paths, leading you to 11B and 22B.
-    Step 2: You choose all of the right paths, leading you to 11Z and 22C.
-    Step 3: You choose all of the left paths, leading you to 11B and 22Z.
-    Step 4: You choose all of the right paths, leading you to 11Z and 22B.
-    Step 5: You choose all of the left paths, leading you to 11B and 22C.
-    Step 6: You choose all of the right paths, leading you to 11Z and 22Z.
-```
+- Step 0: You are at 11A and 22A.
+- Step 1: You choose all of the left paths, leading you to 11B and 22B.
+- Step 2: You choose all of the right paths, leading you to 11Z and 22C.
+- Step 3: You choose all of the left paths, leading you to 11B and 22Z.
+- Step 4: You choose all of the right paths, leading you to 11Z and 22B.
+- Step 5: You choose all of the left paths, leading you to 11B and 22C.
+- Step 6: You choose all of the right paths, leading you to 11Z and 22Z.
 
 So, in this example, you end up entirely on nodes that end in Z after 6 steps.
 
diff --git a/advent-of-code/2023/elixir/day_08/input.txt b/advent-of-code/2023/day_08/input.txt
similarity index 100%
rename from advent-of-code/2023/elixir/day_08/input.txt
rename to advent-of-code/2023/day_08/input.txt
diff --git a/advent-of-code/2023/elixir/day_08/lib/navigator.ex b/advent-of-code/2023/day_08/lib/navigator.ex
similarity index 97%
rename from advent-of-code/2023/elixir/day_08/lib/navigator.ex
rename to advent-of-code/2023/day_08/lib/navigator.ex
index b539a71..cfbdf55 100644
--- a/advent-of-code/2023/elixir/day_08/lib/navigator.ex
+++ b/advent-of-code/2023/day_08/lib/navigator.ex
@@ -7,7 +7,6 @@ defmodule Navigator do
       iex> Navigator.count_steps(["R"], %{"AAA" => ["AAA", "ZZZ"], "ZZZ" => ["ZZZ", "ZZZ"]})
       1
   """
-  @spec count_steps(list(String.t()), map()) :: integer()
   def count_steps(instructions, maps) do
     count_steps(instructions, instructions, maps, "AAA", 0)
   end
diff --git a/advent-of-code/2023/elixir/day_08/lib/parser.ex b/advent-of-code/2023/day_08/lib/parser.ex
similarity index 100%
rename from advent-of-code/2023/elixir/day_08/lib/parser.ex
rename to advent-of-code/2023/day_08/lib/parser.ex
diff --git a/advent-of-code/2023/elixir/day_08/test/navigator_test.exs b/advent-of-code/2023/day_08/lib/task.ex
similarity index 56%
rename from advent-of-code/2023/elixir/day_08/test/navigator_test.exs
rename to advent-of-code/2023/day_08/lib/task.ex
index fe6850e..d79b6f6 100644
--- a/advent-of-code/2023/elixir/day_08/test/navigator_test.exs
+++ b/advent-of-code/2023/day_08/lib/task.ex
@@ -1,16 +1,12 @@
-defmodule NavigatorTest do
-  use ExUnit.Case
-  doctest Navigator
-  doctest Parser
+defmodule Mix.Tasks.Solve do
+  use Mix.Task
 
-  test "part 1" do
+  def run(_) do
     {instructions, maps} = Parser.parse_file("input.txt")
+
     res = Navigator.count_steps(instructions, maps)
     IO.puts("Part 1: #{res}")
-  end
 
-  test "part 2" do
-    {instructions, maps} = Parser.parse_file("input.txt")
     res = Navigator.count_ghost_steps(instructions, maps)
     IO.puts("Part 2: #{res}")
   end
diff --git a/advent-of-code/2023/day_08/mix.exs b/advent-of-code/2023/day_08/mix.exs
new file mode 100644
index 0000000..c855757
--- /dev/null
+++ b/advent-of-code/2023/day_08/mix.exs
@@ -0,0 +1,25 @@
+defmodule Day08.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :day_08,
+      version: "0.1.0",
+      elixir: "~> 1.16",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  defp deps do
+    [
+      {:math, "~> 0.7.0"}
+    ]
+  end
+end
diff --git a/advent-of-code/2023/day_08/mix.lock b/advent-of-code/2023/day_08/mix.lock
new file mode 100644
index 0000000..5823706
--- /dev/null
+++ b/advent-of-code/2023/day_08/mix.lock
@@ -0,0 +1,3 @@
+%{
+  "math": {:hex, :math, "0.7.0", "12af548c3892abf939a2e242216c3e7cbfb65b9b2fe0d872d05c6fb609f8127b", [:mix], [], "hexpm", "7987af97a0c6b58ad9db43eb5252a49fc1dfe1f6d98f17da9282e297f594ebc2"},
+}
diff --git a/advent-of-code/2023/day_08/test/input-1.txt b/advent-of-code/2023/day_08/test/input-1.txt
new file mode 100644
index 0000000..9029a1b
--- /dev/null
+++ b/advent-of-code/2023/day_08/test/input-1.txt
@@ -0,0 +1,9 @@
+RL
+
+AAA = (BBB, CCC)
+BBB = (DDD, EEE)
+CCC = (ZZZ, GGG)
+DDD = (DDD, DDD)
+EEE = (EEE, EEE)
+GGG = (GGG, GGG)
+ZZZ = (ZZZ, ZZZ)
diff --git a/advent-of-code/2023/day_08/test/input-2.txt b/advent-of-code/2023/day_08/test/input-2.txt
new file mode 100644
index 0000000..5b3fa58
--- /dev/null
+++ b/advent-of-code/2023/day_08/test/input-2.txt
@@ -0,0 +1,10 @@
+LR
+
+11A = (11B, XXX)
+11B = (XXX, 11Z)
+11Z = (11B, XXX)
+22A = (22B, XXX)
+22B = (22C, 22C)
+22C = (22Z, 22Z)
+22Z = (22B, 22B)
+XXX = (XXX, XXX)
diff --git a/advent-of-code/2023/day_08/test/navigator_test.exs b/advent-of-code/2023/day_08/test/navigator_test.exs
new file mode 100644
index 0000000..2a415fb
--- /dev/null
+++ b/advent-of-code/2023/day_08/test/navigator_test.exs
@@ -0,0 +1,15 @@
+defmodule NavigatorTest do
+  use ExUnit.Case
+  doctest Navigator
+  doctest Parser
+
+  test "example 1" do
+    {instructions, maps} = Parser.parse_file("test/input-1.txt")
+    assert Navigator.count_steps(instructions, maps) == 2
+  end
+
+  test "example 2" do
+    {instructions, maps} = Parser.parse_file("test/input-2.txt")
+    assert Navigator.count_ghost_steps(instructions, maps) == 6
+  end
+end
diff --git a/advent-of-code/2023/elixir/day_08/test/test_helper.exs b/advent-of-code/2023/day_08/test/test_helper.exs
similarity index 100%
rename from advent-of-code/2023/elixir/day_08/test/test_helper.exs
rename to advent-of-code/2023/day_08/test/test_helper.exs
diff --git a/advent-of-code/2023/elixir/day_09/.formatter.exs b/advent-of-code/2023/day_09/.formatter.exs
similarity index 100%
rename from advent-of-code/2023/elixir/day_09/.formatter.exs
rename to advent-of-code/2023/day_09/.formatter.exs
diff --git a/advent-of-code/2023/elixir/day_09/.gitignore b/advent-of-code/2023/day_09/.gitignore
similarity index 100%
rename from advent-of-code/2023/elixir/day_09/.gitignore
rename to advent-of-code/2023/day_09/.gitignore
diff --git a/advent-of-code/2023/elixir/day_09/README.md b/advent-of-code/2023/day_09/README.md
similarity index 97%
rename from advent-of-code/2023/elixir/day_09/README.md
rename to advent-of-code/2023/day_09/README.md
index 6991ae5..4113a74 100644
--- a/advent-of-code/2023/elixir/day_09/README.md
+++ b/advent-of-code/2023/day_09/README.md
@@ -1,4 +1,8 @@
-# Oasis
+# Advent of Code 2023 day 9 solution in Elixir
+
+## Mirage Maintenance
+
+[Task page](https://adventofcode.com/2023/day/9)
 
 You ride the camel through the sandstorm and stop where the ghost's maps told you to stop.
 The sandstorm subsequently subsides, somehow seeing you standing at an oasis!
@@ -7,7 +11,7 @@ The camel goes to get some water and you stretch your neck.
 As you look up, you discover what must be yet another giant floating island, this one made of metal!
 That must be where the parts to fix the sand machines come from.
 
-There's even a hang glider partially buried in the sand here; once the sun rises and heats up the sand, 
+There's even a hang glider partially buried in the sand here; once the sun rises and heats up the sand,
 you might be able to use the glider and the hot air to get all the way up to the metal island!
 
 While you wait for the sun to rise, you admire the oasis hidden here in the middle of Desert Island.
diff --git a/advent-of-code/2023/elixir/day_09/input.txt b/advent-of-code/2023/day_09/input.txt
similarity index 100%
rename from advent-of-code/2023/elixir/day_09/input.txt
rename to advent-of-code/2023/day_09/input.txt
diff --git a/advent-of-code/2023/elixir/day_09/lib/oasis.ex b/advent-of-code/2023/day_09/lib/oasis.ex
similarity index 66%
rename from advent-of-code/2023/elixir/day_09/lib/oasis.ex
rename to advent-of-code/2023/day_09/lib/oasis.ex
index 943f1f5..971fd20 100644
--- a/advent-of-code/2023/elixir/day_09/lib/oasis.ex
+++ b/advent-of-code/2023/day_09/lib/oasis.ex
@@ -1,30 +1,14 @@
 defmodule Oasis do
-  @moduledoc """
-  Day 9 of Advent of Code 2023.
-
-  Link: https://adventofcode.com/2023/day/9.
-  """
-
-  def solve() do
-    input =
-      File.stream!("input.txt")
-      |> Stream.map(&String.trim_trailing/1)
-      # Get lists of strings.
-      |> Stream.map(&String.split/1)
-      # Get lists of integers.
-      |> Stream.map(fn list -> Enum.map(list, &String.to_integer/1) end)
-
-    # Predict next value for each list.
-    input
-    |> Stream.map(fn list -> predict(list, &predict_next_value/2) end)
+  def get_next_values_sum(lists) do
+    lists
+    |> Stream.map(fn list -> Oasis.predict(list, &Oasis.predict_next_value/2) end)
     |> Enum.sum()
-    |> IO.puts()
+  end
 
-    # Predict previous value for each list.
-    input
-    |> Stream.map(fn list -> predict(list, &predict_prev_value/2) end)
+  def get_prev_values_sum(lists) do
+    lists
+    |> Stream.map(fn list -> Oasis.predict(list, &Oasis.predict_prev_value/2) end)
     |> Enum.sum()
-    |> IO.puts()
   end
 
   @doc """
diff --git a/advent-of-code/2023/day_09/lib/parser.ex b/advent-of-code/2023/day_09/lib/parser.ex
new file mode 100644
index 0000000..50859ed
--- /dev/null
+++ b/advent-of-code/2023/day_09/lib/parser.ex
@@ -0,0 +1,8 @@
+defmodule Parser do
+  def parse(filename) do
+    File.stream!(filename)
+    |> Stream.map(&String.trim_trailing/1)
+    |> Stream.map(&String.split/1)
+    |> Stream.map(fn list -> Enum.map(list, &String.to_integer/1) end)
+  end
+end
diff --git a/advent-of-code/2023/day_09/lib/task.ex b/advent-of-code/2023/day_09/lib/task.ex
new file mode 100644
index 0000000..036f1eb
--- /dev/null
+++ b/advent-of-code/2023/day_09/lib/task.ex
@@ -0,0 +1,13 @@
+defmodule Mix.Tasks.Solve do
+  use Mix.Task
+
+  def run(_) do
+    input = Parser.parse("input.txt")
+
+    res1 = Oasis.get_next_values_sum(input)
+    IO.puts("Part 1: #{res1}")
+
+    res2 = Oasis.get_prev_values_sum(input)
+    IO.puts("Part 2: #{res2}")
+  end
+end
diff --git a/advent-of-code/2023/day_09/mix.exs b/advent-of-code/2023/day_09/mix.exs
new file mode 100644
index 0000000..8fb8d0b
--- /dev/null
+++ b/advent-of-code/2023/day_09/mix.exs
@@ -0,0 +1,23 @@
+defmodule Day09.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :day_09,
+      version: "0.1.0",
+      elixir: "~> 1.16",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  defp deps do
+    []
+  end
+end
diff --git a/advent-of-code/2023/day_09/test/input.txt b/advent-of-code/2023/day_09/test/input.txt
new file mode 100644
index 0000000..539a763
--- /dev/null
+++ b/advent-of-code/2023/day_09/test/input.txt
@@ -0,0 +1,3 @@
+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45
diff --git a/advent-of-code/2023/day_09/test/oasis_test.exs b/advent-of-code/2023/day_09/test/oasis_test.exs
new file mode 100644
index 0000000..0bd0f34
--- /dev/null
+++ b/advent-of-code/2023/day_09/test/oasis_test.exs
@@ -0,0 +1,14 @@
+defmodule OasisTest do
+  use ExUnit.Case
+  doctest Oasis
+
+  test "example 1" do
+    input = Parser.parse("test/input.txt")
+    assert Oasis.get_next_values_sum(input) == 114
+  end
+
+  test "example 2" do
+    input = Parser.parse("test/input.txt")
+    assert Oasis.get_prev_values_sum(input) == 2
+  end
+end
diff --git a/advent-of-code/2023/elixir/day_09/test/test_helper.exs b/advent-of-code/2023/day_09/test/test_helper.exs
similarity index 100%
rename from advent-of-code/2023/elixir/day_09/test/test_helper.exs
rename to advent-of-code/2023/day_09/test/test_helper.exs
diff --git a/advent-of-code/2023/elixir/day_07/test/solution_test.exs b/advent-of-code/2023/elixir/day_07/test/solution_test.exs
deleted file mode 100644
index 29b6724..0000000
--- a/advent-of-code/2023/elixir/day_07/test/solution_test.exs
+++ /dev/null
@@ -1,22 +0,0 @@
-defmodule SolutionTest do
-  use ExUnit.Case
-  doctest Solution
-
-  test "example 1" do
-    assert Solution.get_total_winnings("test/example.txt") == 6440
-  end
-
-  test "part 1" do
-    res = Solution.get_total_winnings("test/input.txt")
-    IO.puts("First answer: #{res}")
-  end
-
-  test "example 2" do
-    assert Solution.get_total_winnings("test/example.txt", true) == 5905
-  end
-
-  test "part 2" do
-    res = Solution.get_total_winnings("test/input.txt", true)
-    IO.puts("Second answer: #{res}")
-  end
-end
diff --git a/advent-of-code/2023/elixir/day_08/mix.exs b/advent-of-code/2023/elixir/day_08/mix.exs
deleted file mode 100644
index 50cbe90..0000000
--- a/advent-of-code/2023/elixir/day_08/mix.exs
+++ /dev/null
@@ -1,30 +0,0 @@
-defmodule Navigator.MixProject do
-  use Mix.Project
-
-  def project do
-    [
-      app: :navigator,
-      version: "0.1.0",
-      elixir: "~> 1.16",
-      start_permanent: Mix.env() == :prod,
-      deps: deps()
-    ]
-  end
-
-  # Run "mix help compile.app" to learn about applications.
-  def application do
-    [
-      extra_applications: [:logger]
-    ]
-  end
-
-  # Run "mix help deps" to learn about dependencies.
-  defp deps do
-    [
-      {:dialyxir, "~> 1.4", only: [:dev, :test], runtime: false},
-      {:math, "~> 0.7.0"}
-      # {: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/advent-of-code/2023/elixir/day_08/mix.lock b/advent-of-code/2023/elixir/day_08/mix.lock
deleted file mode 100644
index b69db76..0000000
--- a/advent-of-code/2023/elixir/day_08/mix.lock
+++ /dev/null
@@ -1,5 +0,0 @@
-%{
-  "dialyxir": {:hex, :dialyxir, "1.4.3", "edd0124f358f0b9e95bfe53a9fcf806d615d8f838e2202a9f430d59566b6b53b", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "bf2cfb75cd5c5006bec30141b131663299c661a864ec7fbbc72dfa557487a986"},
-  "erlex": {:hex, :erlex, "0.2.7", "810e8725f96ab74d17aac676e748627a07bc87eb950d2b83acd29dc047a30595", [:mix], [], "hexpm", "3ed95f79d1a844c3f6bf0cea61e0d5612a42ce56da9c03f01df538685365efb0"},
-  "math": {:hex, :math, "0.7.0", "12af548c3892abf939a2e242216c3e7cbfb65b9b2fe0d872d05c6fb609f8127b", [:mix], [], "hexpm", "7987af97a0c6b58ad9db43eb5252a49fc1dfe1f6d98f17da9282e297f594ebc2"},
-}
diff --git a/advent-of-code/2023/elixir/day_09/mix.exs b/advent-of-code/2023/elixir/day_09/mix.exs
deleted file mode 100644
index 53a4a66..0000000
--- a/advent-of-code/2023/elixir/day_09/mix.exs
+++ /dev/null
@@ -1,28 +0,0 @@
-defmodule Oasis.MixProject do
-  use Mix.Project
-
-  def project do
-    [
-      app: :oasis,
-      version: "0.1.0",
-      elixir: "~> 1.16",
-      start_permanent: Mix.env() == :prod,
-      deps: deps()
-    ]
-  end
-
-  # Run "mix help compile.app" to learn about applications.
-  def application do
-    [
-      extra_applications: [:logger]
-    ]
-  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/advent-of-code/2023/elixir/day_09/test/oasis_test.exs b/advent-of-code/2023/elixir/day_09/test/oasis_test.exs
deleted file mode 100644
index 13d1707..0000000
--- a/advent-of-code/2023/elixir/day_09/test/oasis_test.exs
+++ /dev/null
@@ -1,4 +0,0 @@
-defmodule OasisTest do
-  use ExUnit.Case
-  doctest Oasis
-end