diff --git a/CrystalData.sln b/CrystalData.sln
index b6110bd..79f6788 100644
--- a/CrystalData.sln
+++ b/CrystalData.sln
@@ -3,8 +3,6 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.8.34219.65
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Sandbox", "Sandbox\Sandbox.csproj", "{2B574101-BAE8-4BB9-A8DA-22760EA4BD90}"
-EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{0EAF5544-B4BB-4198-81AB-56835FC8DDED}"
 	ProjectSection(SolutionItems) = preProject
 		.editorconfig = .editorconfig
@@ -16,7 +14,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Advanced", "Advanced\Advanc
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "xUnitTest", "xUnitTest\xUnitTest.csproj", "{460E04B0-4CA5-4672-8BCB-D3D03D07B2D8}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "QuickStart", "QuickStart\QuickStart.csproj", "{B89EE766-400C-4688-BEFA-F242661C8C8A}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "QuickStart", "QuickStart\QuickStart.csproj", "{B89EE766-400C-4688-BEFA-F242661C8C8A}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Playground", "Playground\Playground.csproj", "{F560C481-8D65-4D71-8A68-7F32AC3AAAE0}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -24,10 +24,6 @@ Global
 		Release|Any CPU = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
-		{2B574101-BAE8-4BB9-A8DA-22760EA4BD90}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
-		{2B574101-BAE8-4BB9-A8DA-22760EA4BD90}.Debug|Any CPU.Build.0 = Debug|Any CPU
-		{2B574101-BAE8-4BB9-A8DA-22760EA4BD90}.Release|Any CPU.ActiveCfg = Release|Any CPU
-		{2B574101-BAE8-4BB9-A8DA-22760EA4BD90}.Release|Any CPU.Build.0 = Release|Any CPU
 		{3D362860-ACA2-4192-976D-11DC5DA9AD69}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{3D362860-ACA2-4192-976D-11DC5DA9AD69}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{3D362860-ACA2-4192-976D-11DC5DA9AD69}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -44,6 +40,10 @@ Global
 		{B89EE766-400C-4688-BEFA-F242661C8C8A}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{B89EE766-400C-4688-BEFA-F242661C8C8A}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{B89EE766-400C-4688-BEFA-F242661C8C8A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{F560C481-8D65-4D71-8A68-7F32AC3AAAE0}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{F560C481-8D65-4D71-8A68-7F32AC3AAAE0}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{F560C481-8D65-4D71-8A68-7F32AC3AAAE0}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{F560C481-8D65-4D71-8A68-7F32AC3AAAE0}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
diff --git a/CrystalData/Filer/CrystalFiler.cs b/CrystalData/Filer/CrystalFiler.cs
index 4f4d4be..a7cd092 100644
--- a/CrystalData/Filer/CrystalFiler.cs
+++ b/CrystalData/Filer/CrystalFiler.cs
@@ -1,8 +1,5 @@
 // Copyright (c) All contributors. All rights reserved. Licensed under the MIT license.
 
-using static System.Runtime.InteropServices.JavaScript.JSType;
-using static FastExpressionCompiler.ExpressionCompiler;
-
 namespace CrystalData.Filer;
 
 public class CrystalFiler
@@ -180,9 +177,8 @@ public Task<CrystalResult> LimitNumberOfFiles()
             }
 
             string path;
-            //
             if (!this.crystalFiler.IsProtected)
-            {
+            {// No file history
                 path = this.GetFilePath();
                 var result = await this.rawFiler.ReadAsync(path, 0, -1).ConfigureAwait(false);
                 if (result.IsSuccess)
@@ -191,7 +187,7 @@ public Task<CrystalResult> LimitNumberOfFiles()
                     var r = SerializeHelper.TryDeserialize<TData>(result.Data.Span, formatHint, true);
                     result.Return();
                     if (r.Data is not null)
-                    {
+                    {// Success
                         return (new(CrystalResult.Success, r.Data), new(Waypoint.InvalidJournalPosition, 0, hash), path);
                     }
 
@@ -209,7 +205,7 @@ public Task<CrystalResult> LimitNumberOfFiles()
                 path = this.GetFilePath(x);
                 var result = await this.rawFiler.ReadAsync(path, 0, -1).ConfigureAwait(false);
                 if (result.IsSuccess)
-                {// Success
+                {// Read successful
                     if (FarmHash.Hash64(result.Data.Memory.Span) == x.Hash)
                     {
                         var r = SerializeHelper.TryDeserialize<TData>(result.Data.Span, formatHint, true);
@@ -220,6 +216,7 @@ public Task<CrystalResult> LimitNumberOfFiles()
                         }
                     }
 
+                    // Checksum mismatch or deserialization error.
                     _ = this.rawFiler.DeleteAsync(path);
                     this.TryDeleteWaypoint(x);
                 }
@@ -413,14 +410,14 @@ public async Task<CrystalResult> LimitNumberOfFiles()
 
     public async Task<(CrystalObjectResult<TData> Result, Waypoint Waypoint, string Path)> LoadLatest<TData>(PrepareParam param, SaveFormat formatHint)
         where TData : class, ITinyhandSerialize<TData>, ITinyhandReconstruct<TData>
-    {//
+    {
         if (this.main is null)
         {
             return (new(CrystalResult.NotPrepared), Waypoint.Invalid, string.Empty);
         }
 
         if (!this.IsProtected)
-        {// Not protected
+        {// Not protected (no file history)
             var result = await this.main.LoadLatest<TData>(param, formatHint).ConfigureAwait(false);
             if (result.Result.IsFailure && this.backup is not null)
             {// Load backup
diff --git a/Directory.Build.props b/Directory.Build.props
index d9304c7..53b393b 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
-    <Version>0.16.1</Version>
+    <Version>0.17.0</Version>
     <LangVersion>latest</LangVersion>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
diff --git a/Sandbox/Sandbox.csproj b/Playground/Playground.csproj
similarity index 100%
rename from Sandbox/Sandbox.csproj
rename to Playground/Playground.csproj
diff --git a/Sandbox/Program.cs b/Playground/Program.cs
similarity index 95%
rename from Sandbox/Program.cs
rename to Playground/Program.cs
index a8430f2..7f22abc 100644
--- a/Sandbox/Program.cs
+++ b/Playground/Program.cs
@@ -40,6 +40,7 @@ public static async Task Main(string[] args)
                 context.AddCrystal<FirstData>(
                     new CrystalConfiguration()
                     {
+                        RequiredForLoading = true,
                         SavePolicy = SavePolicy.Manual, // The timing of saving data is controlled by the application.
                         SaveFormat = SaveFormat.Utf8, // The format is utf8 text.
                         NumberOfFileHistories = 0, // No history file.
@@ -58,7 +59,7 @@ public static async Task Main(string[] args)
         var unit = builder.Build(); // Build.
         TinyhandSerializer.ServiceProvider = unit.Context.ServiceProvider;
         var crystalizer = unit.Context.ServiceProvider.GetRequiredService<Crystalizer>(); // Obtains a Crystalizer instance for data storage operations.
-        await crystalizer.PrepareAndLoadAll(false); // Prepare resources for storage operations and read data from files.
+        await crystalizer.PrepareAndLoadAll(true); // Prepare resources for storage operations and read data from files.
 
         var data = unit.Context.ServiceProvider.GetRequiredService<FirstData>(); // Retrieve a data instance from the service provider.