diff --git a/AdventOfCode.lpi b/AdventOfCode.lpi
index 606b61b..de7ba4b 100644
--- a/AdventOfCode.lpi
+++ b/AdventOfCode.lpi
@@ -93,6 +93,10 @@
         <Filename Value="solvers\UParabolicReflectorDish.pas"/>
         <IsPartOfProject Value="True"/>
       </Unit>
+      <Unit>
+        <Filename Value="solvers\ULensLibrary.pas"/>
+        <IsPartOfProject Value="True"/>
+      </Unit>
     </Units>
   </ProjectOptions>
   <CompilerOptions>
diff --git a/AdventOfCode.lpr b/AdventOfCode.lpr
index 338ddf6..583af79 100644
--- a/AdventOfCode.lpr
+++ b/AdventOfCode.lpr
@@ -25,7 +25,7 @@ uses
   {$ENDIF}
   Classes, SysUtils, CustApp, USolver, UTrebuchet, UCubeConundrum, UGearRatios, UScratchcards, UGiveSeedFertilizer,
   UWaitForIt, UCamelCards, UHauntedWasteland, UNumberTheory, UMirageMaintenance, UPipeMaze, UCosmicExpansion,
-  UHotSprings, UPointOfIncidence, UParabolicReflectorDish;
+  UHotSprings, UPointOfIncidence, UParabolicReflectorDish, ULensLibrary;
 
 type
 
@@ -64,6 +64,7 @@ begin
   engine.RunAndFree(THotSprings.Create);
   engine.RunAndFree(TPointOfIncidence.Create);
   engine.RunAndFree(TParabolicReflectorDish.Create);
+  engine.RunAndFree(TLensLibrary.Create);
   engine.Free;
 end;
 
diff --git a/solvers/ULensLibrary.pas b/solvers/ULensLibrary.pas
new file mode 100644
index 0000000..d6831d7
--- /dev/null
+++ b/solvers/ULensLibrary.pas
@@ -0,0 +1,80 @@
+{
+  Solutions to the Advent Of Code.
+  Copyright (C) 2023  Stefan Müller
+
+  This program is free software: you can redistribute it and/or modify it under
+  the terms of the GNU General Public License as published by the Free Software
+  Foundation, either version 3 of the License, or (at your option) any later
+  version.
+
+  This program is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  this program.  If not, see <http://www.gnu.org/licenses/>.
+}
+
+unit ULensLibrary;
+
+{$mode ObjFPC}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, USolver;
+
+type
+
+  { TLensLibrary }
+
+  TLensLibrary = class(TSolver)
+  private
+    function CalcHash(const AInput: string): Byte;
+  public
+    procedure ProcessDataLine(const ALine: string); override;
+    procedure Finish; override;
+    function GetDataFileName: string; override;
+    function GetPuzzleName: string; override;
+  end;
+
+implementation
+
+{ TLensLibrary }
+
+function TLensLibrary.CalcHash(const AInput: string): Byte;
+var
+  c: Char;
+begin
+  Result := 0;
+  for c in AInput do
+    Result := ((Result + Ord(c)) * 17) and 255;
+end;
+
+procedure TLensLibrary.ProcessDataLine(const ALine: string);
+var
+  split: TStringArray;
+  s: string;
+begin
+  split := ALine.Split(',');
+  for s in split do
+    Inc(FPart1, CalcHash(s));
+end;
+
+procedure TLensLibrary.Finish;
+begin
+
+end;
+
+function TLensLibrary.GetDataFileName: string;
+begin
+  Result := 'lens_library.txt';
+end;
+
+function TLensLibrary.GetPuzzleName: string;
+begin
+  Result := 'Day 15: Lens Library';
+end;
+
+end.
+
diff --git a/tests/AdventOfCodeFPCUnit.lpi b/tests/AdventOfCodeFPCUnit.lpi
index bc6bfbd..eedd017 100644
--- a/tests/AdventOfCodeFPCUnit.lpi
+++ b/tests/AdventOfCodeFPCUnit.lpi
@@ -100,6 +100,10 @@
         <Filename Value="UParabolicReflectorDishTestCases.pas"/>
         <IsPartOfProject Value="True"/>
       </Unit>
+      <Unit>
+        <Filename Value="ULensLibraryTestCases.pas"/>
+        <IsPartOfProject Value="True"/>
+      </Unit>
     </Units>
   </ProjectOptions>
   <CompilerOptions>
diff --git a/tests/AdventOfCodeFPCUnit.lpr b/tests/AdventOfCodeFPCUnit.lpr
index 08a515b..ab3a37c 100644
--- a/tests/AdventOfCodeFPCUnit.lpr
+++ b/tests/AdventOfCodeFPCUnit.lpr
@@ -5,8 +5,8 @@ program AdventOfCodeFPCUnit;
 uses
   Interfaces, Forms, GuiTestRunner, USolver, UBaseTestCases, UTrebuchetTestCases, UCubeConundrumTestCases,
   UGearRatiosTestCases, UScratchcardsTestCases, UGiveSeedFertilizerTestCases, UWaitForItTestCases, UCamelCardsTestCases,
-  UHauntedWastelandTestCases, UMirageMaintenanceTestCases, UPipeMazeTestCases, UCosmicExpansionTestCases, 
-  UHotSpringsTestCases, UPointOfIncidenceTestCases, UParabolicReflectorDishTestCases;
+  UHauntedWastelandTestCases, UMirageMaintenanceTestCases, UPipeMazeTestCases, UCosmicExpansionTestCases,
+  UHotSpringsTestCases, UPointOfIncidenceTestCases, UParabolicReflectorDishTestCases, ULensLibraryTestCases;
 
 {$R *.res}
 
diff --git a/tests/ULensLibraryTestCases.pas b/tests/ULensLibraryTestCases.pas
new file mode 100644
index 0000000..f22a345
--- /dev/null
+++ b/tests/ULensLibraryTestCases.pas
@@ -0,0 +1,78 @@
+{
+  Solutions to the Advent Of Code.
+  Copyright (C) 2023  Stefan Müller
+
+  This program is free software: you can redistribute it and/or modify it under
+  the terms of the GNU General Public License as published by the Free Software
+  Foundation, either version 3 of the License, or (at your option) any later
+  version.
+
+  This program is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  this program.  If not, see <http://www.gnu.org/licenses/>.
+}
+
+unit ULensLibraryTestCases;
+
+{$mode ObjFPC}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, fpcunit, testregistry, USolver, UBaseTestCases, ULensLibrary;
+
+type
+
+  { TLensLibraryFullDataTestCase }
+
+  TLensLibraryFullDataTestCase = class(TEngineBaseTest)
+  protected
+    function CreateSolver: ISolver; override;
+  published
+    procedure TestPart1;
+  end;
+
+  { TLensLibraryExampleTestCase }
+
+  TLensLibraryExampleTestCase = class(TExampleEngineBaseTest)
+  protected
+    function CreateSolver: ISolver; override;
+  published
+    procedure TestPart1;
+  end;
+
+implementation
+
+{ TLensLibraryFullDataTestCase }
+
+function TLensLibraryFullDataTestCase.CreateSolver: ISolver;
+begin
+  Result := TLensLibrary.Create;
+end;
+
+procedure TLensLibraryFullDataTestCase.TestPart1;
+begin
+  AssertEquals(519041, FSolver.GetResultPart1);
+end;
+
+{ TLensLibraryExampleTestCase }
+
+function TLensLibraryExampleTestCase.CreateSolver: ISolver;
+begin
+  Result := TLensLibrary.Create;
+end;
+
+procedure TLensLibraryExampleTestCase.TestPart1;
+begin
+  AssertEquals(1320, FSolver.GetResultPart1);
+end;
+
+initialization
+
+  RegisterTest(TLensLibraryFullDataTestCase);
+  RegisterTest(TLensLibraryExampleTestCase);
+end.
+