diff --git a/13/PointOfIncidence.Tests/PatternTests.cs b/13/PointOfIncidence.Tests/PatternTests.cs
new file mode 100644
index 0000000..5022129
--- /dev/null
+++ b/13/PointOfIncidence.Tests/PatternTests.cs
@@ -0,0 +1,160 @@
+namespace PointOfIncidence.Tests;
+
+public class PatternTests
+{
+  [Theory]
+  [MemberData(nameof(TestData.ParseTestData), MemberType = typeof(TestData))]
+  public void Parse_GivenAPattern_ItShouldReturnPatternInstance(string[] input, Pattern expected)
+  {
+    var result = Pattern.Parse(input);
+    result.Should().BeEquivalentTo(expected);
+  }
+
+  [Theory]
+  [MemberData(nameof(TestData.FindPointOfReflectionTestData), MemberType = typeof(TestData))]
+  public void FindPointOfReflection_GivenAPattern_ItShouldReturnPointOfReflection(string[] input, PointOfReflection expected)
+  {
+    var pattern = Pattern.Parse(input);
+    var result = pattern.FindPointOfReflection();
+    result.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void SummarizePatternNotes_GivenExampleInput_ItShouldReturnExpectedValue()
+  {
+    var input = File
+      .ReadAllText("EXAMPLE.txt")
+      .ReplaceLineEndings();
+
+    var patterns = input
+      .Split(Environment.NewLine + Environment.NewLine)
+      .Select(p => p.Split(Environment.NewLine));
+
+    var result = patterns
+      .Select(Pattern.Parse)
+      .Sum(p => p.SummarizePatternNotes());
+
+    result.Should().Be(405);
+  }
+
+
+  [Fact]
+  public void SummarizePatternNotes_GivenInput_ItShouldReturnExpectedValue()
+  {
+    var input = File
+      .ReadAllText("INPUT.txt")
+      .ReplaceLineEndings();
+
+    var patterns = input
+      .Split(Environment.NewLine + Environment.NewLine)
+      .Select(p => p.Split(Environment.NewLine));
+
+    var result = patterns
+      .Select(Pattern.Parse)
+      .Select(p => p.SummarizePatternNotes())
+      .Sum();
+
+    result.Should().Be(33728);
+  }
+
+  public static class TestData
+  {
+    public static IEnumerable<object[]> ParseTestData =>
+      new List<object[]>
+      {
+        new object[]
+        {
+          new string[]
+          {
+            "#.##..##.",
+            "..#.##.#.",
+          },
+          new Pattern(
+            [
+              ['#', '.', '#', '#', '.', '.', '#', '#', '.'],
+              ['.', '.', '#', '.', '#', '#', '.', '#', '.'],
+            ],
+            [
+              ['#', '.'],
+              ['.', '.'],
+              ['#', '#'],
+              ['#', '.'],
+              ['.', '#'],
+              ['.', '#'],
+              ['#', '.'],
+              ['#', '#'],
+              ['.', '.'],
+            ]
+          ),
+        }
+      };
+
+    public static IEnumerable<object[]> FindPointOfReflectionTestData =>
+      new List<object[]>
+      {
+        new object[]
+        {
+          new string[]
+          {
+            "#...##..#",
+            "#....#..#",
+            "..##..###",
+            "#####.##.",
+            "#####.##.",
+            "..##..###",
+            "#....#..#",
+          },
+          new PointOfReflection
+          {
+            Type = ReflectionType.Horizontal,
+            StartIndex = 3,
+            EndIndex = 4,
+          },
+        },
+        new object[]
+        {
+          new string[]
+          {
+            "#.##..##.",
+            "..#.##.#.",
+            "##......#",
+            "##......#",
+            "..#.##.#.",
+            "..##..##.",
+            "#.#.##.#.",
+          },
+          new PointOfReflection
+          {
+            Type = ReflectionType.Vertical,
+            StartIndex = 4,
+            EndIndex = 5,
+          }
+        },
+        new object[]
+        {
+          new string[]
+          {
+            "...##..##.#.#",
+            ".##.#####.###",
+            "##.#....####.",
+            "#.#....#.#..#",
+            ".#..#.#...#.#",
+            ".#..#.#...#.#",
+            "#.#....#.#..#",
+            "##.#....####.",
+            ".########.###",
+            "...##..##.#.#",
+            "#.#.###.....#",
+            "#.#.###.....#",
+            "...##..##.#.#",
+          },
+          new PointOfReflection
+          {
+            Type = ReflectionType.Horizontal,
+            StartIndex = 10,
+            EndIndex = 11,
+          },
+        },
+      };
+  }
+}
\ No newline at end of file
diff --git a/13/PointOfIncidence.Tests/PointOfIncidence.Tests.csproj b/13/PointOfIncidence.Tests/PointOfIncidence.Tests.csproj
index 8c7a13b..21b4499 100644
--- a/13/PointOfIncidence.Tests/PointOfIncidence.Tests.csproj
+++ b/13/PointOfIncidence.Tests/PointOfIncidence.Tests.csproj
@@ -27,4 +27,16 @@
     <ProjectReference Include="..\PointOfIncidence\PointOfIncidence.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <Content Include="..\INPUT.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include=".\EXAMPLE.txt">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
 </Project>
diff --git a/13/PointOfIncidence.Tests/UnitTest1.cs b/13/PointOfIncidence.Tests/UnitTest1.cs
deleted file mode 100644
index df19976..0000000
--- a/13/PointOfIncidence.Tests/UnitTest1.cs
+++ /dev/null
@@ -1,10 +0,0 @@
-namespace PointOfIncidence.Tests;
-
-public class UnitTest1
-{
-    [Fact]
-    public void Test1()
-    {
-
-    }
-}
\ No newline at end of file
diff --git a/13/PointOfIncidence/Program.cs b/13/PointOfIncidence/Program.cs
index 3751555..0c67213 100644
--- a/13/PointOfIncidence/Program.cs
+++ b/13/PointOfIncidence/Program.cs
@@ -1,2 +1,212 @@
-// See https://aka.ms/new-console-template for more information
-Console.WriteLine("Hello, World!");
+using System.Diagnostics;
+
+namespace PointOfIncidence;
+
+public class Program
+{
+  public static async Task<int> Main(string[] args)
+  {
+    if (args.Length is 0)
+    {
+      Console.WriteLine("Please provide a path to the input file.");
+      return -1;
+    }
+
+    if (File.Exists(args[0]) is false)
+    {
+      Console.WriteLine("The provided file does not exist.");
+      return -2;
+    }
+
+    var input = await File.ReadAllTextAsync(args[0]);
+
+    var patterns = input
+      .ReplaceLineEndings()
+      .Split(Environment.NewLine + Environment.NewLine)
+      .Select(p => p.Split(Environment.NewLine));
+
+    var stopwatch = new Stopwatch();
+    stopwatch.Start();
+
+    var result = patterns
+      .Select(Pattern.Parse)
+      .Sum(p => p.SummarizePatternNotes());
+
+    stopwatch.Stop();
+
+    Console.WriteLine($"The total of all pattern note summaries is {result}. ({stopwatch.ElapsedMilliseconds}ms)");
+
+    return (int)result;
+  }
+}
+
+public class Pattern(
+  List<List<char>> rows,
+  List<List<char>> columns
+)
+{
+  public List<List<char>> Rows { get; init; } = rows;
+  public List<List<char>> Columns { get; init; } = columns;
+
+  public PointOfReflection FindPointOfReflection()
+  {
+    var pointOfReflection = new PointOfReflection();
+    var startRowIndex = 0;
+    var endRowIndex = 1;
+
+    while (endRowIndex < Rows.Count)
+    {
+      var startRow = Rows[startRowIndex];
+      var endRow = Rows[endRowIndex];
+
+      if (startRow.SequenceEqual(endRow))
+      {
+        var isHorizontalReflection = true;
+        var possibleReflectionPoint = new PointOfReflection
+        {
+          StartIndex = startRowIndex,
+          EndIndex = endRowIndex,
+          Type = ReflectionType.Horizontal,
+        };
+
+        while (startRowIndex > 0 && endRowIndex < Rows.Count - 1)
+        {
+          var previousRow = Rows[startRowIndex - 1];
+          var nextRow = Rows[endRowIndex + 1];
+
+          if (previousRow.SequenceEqual(nextRow) is false)
+          {
+            isHorizontalReflection = false;
+            startRowIndex = possibleReflectionPoint.StartIndex;
+            endRowIndex = possibleReflectionPoint.EndIndex;
+            break;
+          }
+
+          startRowIndex--;
+          endRowIndex++;
+        }
+
+        if (isHorizontalReflection)
+        {
+          pointOfReflection = possibleReflectionPoint;
+          break;
+        }
+      }
+
+      startRowIndex++;
+      endRowIndex++;
+    }
+
+    if (pointOfReflection.Type == ReflectionType.None)
+    {
+      var startColumnIndex = 0;
+      var endColumnIndex = 1;
+
+      while (endColumnIndex < Columns.Count)
+      {
+        var startColumn = Columns[startColumnIndex];
+        var endColumn = Columns[endColumnIndex];
+
+        if (startColumn.SequenceEqual(endColumn))
+        {
+          var isVerticalReflection = true;
+          var possibleReflectionPoint = new PointOfReflection
+          {
+            StartIndex = startColumnIndex,
+            EndIndex = endColumnIndex,
+            Type = ReflectionType.Vertical,
+          };
+
+          while (startColumnIndex > 0 && endColumnIndex < Columns.Count - 1)
+          {
+            var previousColumn = Columns[startColumnIndex - 1];
+            var nextColumn = Columns[endColumnIndex + 1];
+
+            if (previousColumn.SequenceEqual(nextColumn) is false)
+            {
+              isVerticalReflection = false;
+              startColumnIndex = possibleReflectionPoint.StartIndex;
+              endColumnIndex = possibleReflectionPoint.EndIndex;
+              break;
+            }
+
+            startColumnIndex--;
+            endColumnIndex++;
+          }
+
+          if (isVerticalReflection)
+          {
+            pointOfReflection = possibleReflectionPoint;
+            break;
+          }
+        }
+
+        startColumnIndex++;
+        endColumnIndex++;
+      }
+    }
+
+    return pointOfReflection;
+  }
+
+  public long SummarizePatternNotes()
+  {
+    var pointOfReflection = FindPointOfReflection();
+
+    if (pointOfReflection.Type is ReflectionType.None)
+    {
+      return 0;
+    }
+
+    if (pointOfReflection.Type is ReflectionType.Vertical)
+    {
+      return pointOfReflection.StartIndex + 1;
+    }
+
+    return (pointOfReflection.StartIndex + 1) * 100;
+  }
+
+  public static Pattern Parse(string[] input)
+  {
+    var columns = new List<List<char>>();
+
+    var height = input.Length;
+    var width = input[0].Length;
+
+    for (var i = 0; i < width; i++)
+    {
+      var column = new List<char>();
+
+      for (var j = 0; j < height; j++)
+      {
+        column.Add(input[j][i]);
+      }
+
+      columns.Add(column);
+    }
+
+    var rows = input
+      .Select(
+        row => row
+          .ToCharArray()
+          .ToList()
+      )
+      .ToList();
+
+    return new Pattern(rows, columns);
+  }
+}
+
+public class PointOfReflection
+{
+  public ReflectionType Type = ReflectionType.None;
+  public int StartIndex { get; set; } = -1;
+  public int EndIndex { get; set; } = -1;
+}
+
+public enum ReflectionType
+{
+  Horizontal,
+  Vertical,
+  None,
+}
\ No newline at end of file