diff --git a/2023/README.md b/2023/README.md
index dca55fa..094313d 100644
--- a/2023/README.md
+++ b/2023/README.md
@@ -1,12 +1,12 @@
 # Advent of Code 2023
 
-|  S  |  M  |  T  |  W  |  T  |  F  |              S              |
-| :-: | :-: | :-: | :-: | :-: | :-: | :-------------------------: |
-|     |     |     |     |     | [1] |             [2]             |
-| [3] | [4] | [5] |  6  | [7] | [8] | [9]<sup>[haskell][9h]</sup> |
-| 10  | [11]  | 12  | 13  | 14  | 15  |              16             |
-| 17  | 18  | 19  | 20  | 21  | 22  |              23             |
-| 24  | 25  |     |     |     |     |                             |
+|  S  |  M   |  T  |  W   |  T  |  F  |              S              |
+| :-: | :-:  | :-: | :-:  | :-: | :-: | :-------------------------: |
+|     |      |     |      |     | [1] |             [2]             |
+| [3] | [4]  | [5] |  6   | [7] | [8] | [9]<sup>[haskell][9h]</sup> |
+| 10  | [11] | 12  | [13] | 14  | 15  |              16             |
+| 17  | 18   | 19  | 20   | 21  | 22  |              23             |
+| 24  | 25   |     |      |     |     |                             |
 
 [1]: ./lib/2023/1.ex
 [2]: ./lib/2023/2.ex
@@ -22,3 +22,5 @@
 [9h]: ./9.hs
 
 [11]: ./lib/2023/11.ex
+
+[13]: ./lib/2023/13.ex
diff --git a/2023/lib/2023/13.ex b/2023/lib/2023/13.ex
new file mode 100644
index 0000000..5fb2c3b
--- /dev/null
+++ b/2023/lib/2023/13.ex
@@ -0,0 +1,44 @@
+import AOC
+import AOCHelpers
+
+aoc 2023, 13 do
+  def p1(input) do
+    input
+    |> String.split("\n\n")
+    |> Enum.map(&lines_of_chars/1)
+    |> Enum.map(&summarize/1)
+    |> Enum.sum()
+  end
+
+  def p2(_input) do
+  end
+
+  def summarize(lines) do
+    vertical_line_of_reflection = find_reflection_index(lines)
+    horizontal_line_of_reflection = lines |> transpose() |> find_reflection_index()
+
+    summary = vertical_line_of_reflection + 100 * horizontal_line_of_reflection
+
+    summary
+  end
+
+  def find_reflection_index(lines) do
+    len = lines |> List.first() |> length()
+
+    idx =
+      for i <- 1..(len - 1) do
+        lines
+        |> Enum.all?(fn line ->
+          line
+          |> Enum.split(i)
+          |> Tuple.to_list()
+          |> map_list([&Enum.reverse/1, &id/1])
+          |> Enum.zip_with(&apply(Kernel, :==, &1))
+          |> Enum.all?(is?(true))
+        end)
+      end
+      |> Enum.find_index(is?(true))
+
+    if idx, do: idx + 1, else: 0
+  end
+end
diff --git a/2023/lib/aoc_helpers.ex b/2023/lib/aoc_helpers.ex
index cdda4a3..fa90c04 100644
--- a/2023/lib/aoc_helpers.ex
+++ b/2023/lib/aoc_helpers.ex
@@ -7,10 +7,12 @@ defmodule AOCHelpers do
     String.split(str)
   end
 
-  def letters(str) when is_binary(str) do
+  def chars(str) when is_binary(str) do
     String.split(str, "", trim: true)
   end
 
+  def letters(str), do: chars(str)
+
   def integers(str) when is_binary(str) do
     str
     |> words()
@@ -27,6 +29,12 @@ defmodule AOCHelpers do
     |> Enum.map(&integers/1)
   end
 
+  def lines_of_chars(input) do
+    input
+    |> lines()
+    |> Enum.map(&chars/1)
+  end
+
   def to_grid(str) do
     lists =
       str
@@ -77,4 +85,10 @@ defmodule AOCHelpers do
   def combinations([x | xs], n) do
     for(tail <- combinations(xs, n - 1), do: [x | tail]) ++ combinations(xs, n)
   end
+
+  def transpose(list_of_lists) do
+    list_of_lists
+    |> Enum.zip()
+    |> Enum.map(&Tuple.to_list/1)
+  end
 end
diff --git a/README.md b/README.md
index bbf2052..e2b4e09 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@
 1. [2020] **17/50** 🌟
 1. [2021] **43/50** 🌟
 1. [2022] **14/50** 🌟
-1. [2023] **17/50** 🌟
+1. [2023] **18/50** 🌟
 
 [2015]: ./2015
 [2017]: ./2017