diff --git a/BallanceTasEditor/BallanceTasEditor/Backend/FpsConverter.cs b/BallanceTasEditor/BallanceTasEditor/Backend/FpsConverter.cs
index 4349251..c2cd032 100644
--- a/BallanceTasEditor/BallanceTasEditor/Backend/FpsConverter.cs
+++ b/BallanceTasEditor/BallanceTasEditor/Backend/FpsConverter.cs
@@ -9,6 +9,31 @@ namespace BallanceTasEditor.Backend {
     /// FPS converter
     /// </summary>
     public static class FpsConverter {
+        /// <summary>
+        /// Check if the FPS is valid
+        /// </summary>
+        /// <param name="fps">FPS in integer</param>
+        /// <returns>Is valid</returns>
+        public static bool IsValidFps(uint fps) {
+            return fps > 0;
+        }
+        /// <summary>
+        /// Check if the FPS is valid
+        /// </summary>
+        /// <param name="fps">FPS in float point</param>
+        /// <returns>Is valid</returns>
+        public static bool IsValidFps(float fps) {
+            return fps > 0;
+        }
+        /// <summary>
+        /// Check if the delta time is valid
+        /// </summary>
+        /// <param name="delta">Delta time in float point</param>
+        /// <returns>Is valid</returns>
+        public static bool IsValidDelta(float delta) {
+            return delta > 0;
+        }
+
         /// <summary>
         /// Convert float point delta time to float point FPS
         /// </summary>
diff --git a/BallanceTasEditor/BallanceTasEditor/Backend/TasClipboard.cs b/BallanceTasEditor/BallanceTasEditor/Backend/TasClipboard.cs
index 7fa7a2f..9070a66 100644
--- a/BallanceTasEditor/BallanceTasEditor/Backend/TasClipboard.cs
+++ b/BallanceTasEditor/BallanceTasEditor/Backend/TasClipboard.cs
@@ -35,14 +35,14 @@ namespace BallanceTasEditor.Backend {
             return GetClipboardObject() is not null;
         }
 
-        public static EnumerableArray? GetClipboard() {
+        public static IExactSizeEnumerable<TasFrame>? GetClipboard() {
             var rawFrames = GetClipboardObject();
             if (rawFrames is null) return null;
 
             return new EnumerableArray(rawFrames);
         }
 
-        public sealed class EnumerableArray : IExactSizeEnumerable<TasFrame> {
+        private sealed class EnumerableArray : IExactSizeEnumerable<TasFrame> {
             public EnumerableArray(RawTasFrame[] rawFrames) {
                 m_RawFrames = rawFrames;
             }
diff --git a/BallanceTasEditor/BallanceTasEditor/Backend/TasFrame.cs b/BallanceTasEditor/BallanceTasEditor/Backend/TasFrame.cs
index d85e78e..3a907b0 100644
--- a/BallanceTasEditor/BallanceTasEditor/Backend/TasFrame.cs
+++ b/BallanceTasEditor/BallanceTasEditor/Backend/TasFrame.cs
@@ -46,6 +46,10 @@ namespace BallanceTasEditor.Backend {
         public const int MIN_KEY_INDEX = 0;
         public const int MAX_KEY_INDEX = 8;
 
+        public static bool IsValidIndex(int index) {
+            return index >= MIN_KEY_INDEX && index <= MAX_KEY_INDEX;
+        }
+
         public static TasKey FromIndex(int index) {
             if (index < MIN_KEY_INDEX || index > MAX_KEY_INDEX) {
                 throw new ArgumentOutOfRangeException(nameof(index));
diff --git a/BallanceTasEditor/BallanceTasEditor/Backend/TasOperation.cs b/BallanceTasEditor/BallanceTasEditor/Backend/TasOperation.cs
index 651afd1..558178e 100644
--- a/BallanceTasEditor/BallanceTasEditor/Backend/TasOperation.cs
+++ b/BallanceTasEditor/BallanceTasEditor/Backend/TasOperation.cs
@@ -51,6 +51,11 @@ namespace BallanceTasEditor.Backend {
         int Occupation();
     }
 
+    internal static class OperationExceptions {
+        internal static readonly InvalidOperationException ExecutionEnvironment = new InvalidOperationException("Can not execute one TAS operation multiple times.");
+        internal static readonly InvalidOperationException RevokeEnvironment = new InvalidOperationException("Can not revoke an not executed TAS operation.");
+    }
+
     public enum CellKeysOperationKind {
         Set, Unset, Flip
     }
@@ -88,7 +93,7 @@ namespace BallanceTasEditor.Backend {
 
         public void Execute(ITasSequence seq) {
             if (m_FramesBackup is not null) {
-                throw new InvalidOperationException("Can not execute one TAS operation multiple times.");
+                throw OperationExceptions.ExecutionEnvironment;
             }
 
             // Check index range.
@@ -126,7 +131,7 @@ namespace BallanceTasEditor.Backend {
 
         public void Revoke(ITasSequence seq) {
             if (m_FramesBackup is null) {
-                throw new InvalidOperationException("Can not revoke an not executed TAS operation.");
+                throw OperationExceptions.RevokeEnvironment;
             }
 
             // Index range is checked,
@@ -185,8 +190,10 @@ namespace BallanceTasEditor.Backend {
     public class AddFrameOperation : ITasRevocableOperation {
         public AddFrameOperation(int index, uint fps, int count) {
             // Check argument
+            if (!FpsConverter.IsValidFps(fps)) {
+                throw new ArgumentOutOfRangeException(nameof(fps));
+            }
             ArgumentOutOfRangeException.ThrowIfNegative(count);
-            ArgumentOutOfRangeException.ThrowIfZero(fps);
             // Assign argument
             m_Index = index;
             m_Fps = fps;
@@ -205,17 +212,20 @@ namespace BallanceTasEditor.Backend {
 
         public void Execute(ITasSequence seq) {
             if (m_IsExecuted) {
-                throw new InvalidOperationException("Can not execute one TAS operation multiple times.");
+                throw OperationExceptions.ExecutionEnvironment;
             }
 
             // Check argument.
             ArgumentOutOfRangeException.ThrowIfGreaterThan(m_Index, seq.GetCount());
 
-            // Prepare data builder.
-            var iter = Enumerable.Range(0, m_Count).Select((_) => TasFrame.FromFps(m_Fps));
-            var exactSizedIter = new ExactSizeEnumerableAdapter<TasFrame>(iter, m_Count);
-            // Execute inserting.
-            seq.Insert(m_Index, exactSizedIter);
+            // Skip if count is zero.
+            if (m_Count != 0) {
+                // Prepare data builder.
+                var iter = Enumerable.Range(0, m_Count).Select((_) => TasFrame.FromFps(m_Fps));
+                var exactSizedIter = new ExactSizeEnumerableAdapter<TasFrame>(iter, m_Count);
+                // Execute inserting.
+                seq.Insert(m_Index, exactSizedIter);
+            }
 
             // Set status
             m_IsExecuted = true;
@@ -223,14 +233,13 @@ namespace BallanceTasEditor.Backend {
 
         public void Revoke(ITasSequence seq) {
             if (!m_IsExecuted) {
-                throw new InvalidOperationException("Can not revoke an not executed TAS operation.");
+                throw OperationExceptions.RevokeEnvironment;
             }
 
-            // If we inserted count is not zero, remove inserted frames
+            // Arguments were checked so we directly resotre them.
+            // If we inserted count is not zero, remove inserted frames, otherwise do nothing.
             if (m_Count != 0) {
                 seq.Remove(m_Index, m_Index + m_Count - 1);
-            } else {
-                // Otherwise just skip it.
             }
             // Modify execution status
             m_IsExecuted = false;
@@ -269,7 +278,7 @@ namespace BallanceTasEditor.Backend {
         public void Execute(ITasSequence seq) {
             // Check execution status first.
             if (m_IsExecuted) {
-                throw new InvalidOperationException("Can not execute one TAS operation multiple times.");
+                throw OperationExceptions.ExecutionEnvironment;
             }
             // Execute operation
             foreach (var frame in seq) {
@@ -295,7 +304,7 @@ namespace BallanceTasEditor.Backend {
         public void Execute(ITasSequence seq) {
             // Check execution status first.
             if (m_IsExecuted) {
-                throw new InvalidOperationException("Can not execute one TAS operation multiple times.");
+                throw OperationExceptions.ExecutionEnvironment;
             }
             // Execute operation
             foreach (var frame in seq) {