diff --git a/WanaKanaShaapu/Constants.cs b/WanaKanaShaapu/Constants.cs
index 17a4d3c..9481484 100644
--- a/WanaKanaShaapu/Constants.cs
+++ b/WanaKanaShaapu/Constants.cs
@@ -1,4 +1,6 @@
-namespace WanaKanaShaapu
+using System.Collections.Generic;
+
+namespace WanaKanaShaapu
 {
     public static class Constants
     {
@@ -53,11 +55,11 @@ public static class Constants
 
         readonly public static CharacterRange[] MacronCharacterRanges = new CharacterRange[]
         {
-            new('\u0100', '\u0101'),
-            new('\u0112', '\u0113'),
-            new('\u012a', '\u012b'),
-            new('\u014C', '\u014D'),    
-            new('\u016A', '\u016B')
+            new CharacterRange('\u0100', '\u0101'),
+            new CharacterRange('\u0112', '\u0113'),
+            new CharacterRange('\u012a', '\u012b'),
+            new CharacterRange('\u014C', '\u014D'),    
+            new CharacterRange('\u016A', '\u016B')
         };
 
         readonly public static CharacterRange[] KanaCharacterRanges = new CharacterRange[]
@@ -192,7 +194,7 @@ public static class Constants
             "ヵ"
         };
 
-        public static Dictionary<char, string> SokuonWhitelist = new()
+        public static Dictionary<char, string> SokuonWhitelist = new Dictionary<char, string>()
         {
             { 'b', "b" },
             { 'c', "t" },
@@ -214,7 +216,7 @@ public static class Constants
             { 'z', "z" }
         };
 
-        public static Dictionary<string, (string Romaji, string Kana)[]> BasicKunrei = new ()
+        public static Dictionary<string, (string Romaji, string Kana)[]> BasicKunrei = new Dictionary<string, (string Romaji, string Kana)[]>()
         {
             { "a", new (string Romaji, string Kana)[] { ("", "あ") } },
             { "i", new (string Romaji, string Kana)[] { ("", "い") } },
diff --git a/WanaKanaShaapu/DefaultOptions.cs b/WanaKanaShaapu/DefaultOptions.cs
index 9854e45..429b2b9 100644
--- a/WanaKanaShaapu/DefaultOptions.cs
+++ b/WanaKanaShaapu/DefaultOptions.cs
@@ -1,4 +1,6 @@
-namespace WanaKanaShaapu
+using System.Collections.Generic;
+
+namespace WanaKanaShaapu
 {
     public class DefaultOptions
     {
@@ -8,7 +10,7 @@ public class DefaultOptions
         public bool UpcaseKatakana { get; set; }
         public dynamic IMEMode { get; set; }
         public string Romanization { get; set; } = "hepburn";
-        public Dictionary<string, string> CustomKanaMapping = new();
-        public Dictionary<string, string> CustomRomajiMapping = new();
+        public Dictionary<string, string> CustomKanaMapping = new Dictionary<string, string>();
+        public Dictionary<string, string> CustomRomajiMapping = new Dictionary<string, string>();
     }
 }
\ No newline at end of file
diff --git a/WanaKanaShaapu/Internal/Utils.cs b/WanaKanaShaapu/Internal/Utils.cs
index 50ecaa0..37aaec0 100644
--- a/WanaKanaShaapu/Internal/Utils.cs
+++ b/WanaKanaShaapu/Internal/Utils.cs
@@ -1,9 +1,16 @@
-using System.Runtime.InteropServices;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
 
 namespace WanaKanaShaapu.Internal
 {
     internal static class Utils
     {
+        internal static bool IsAscii(char c)
+        {
+            return c >= 0 && c <= 127;
+        }
         internal static bool IsMacron(char c)
         {
             foreach (var range in Constants.MacronCharacterRanges)
@@ -89,7 +96,7 @@ internal static string GetTokenTypeCompact(char c)
             string letter = c.ToString();
             if (WanaKana.IsJapanese(letter) && (Char.IsLetter(c) || Char.IsWhiteSpace(c)))
                 return "ja";
-            else if (Char.IsAscii(c) && (Char.IsLetter(c) || Char.IsWhiteSpace(c)))
+            else if (IsAscii(c) && (Char.IsLetter(c) || Char.IsWhiteSpace(c)))
                 return "en";
             else
                 return "other";
@@ -116,9 +123,9 @@ internal static string GetTokenType(char c, string previousType, bool compact)
                 return "japanesePunctuation";
             else if (WanaKana.IsJapanese(letter))
                 return "ja";
-            else if (Char.IsAscii(c) && Char.IsLetter(c))
+            else if (IsAscii(c) && Char.IsLetter(c))
                 return "en";
-            else if (Char.IsDigit(c) && Char.IsAscii(c))
+            else if (Char.IsDigit(c) && IsAscii(c))
                 return "englishNumeral";
             else if (Char.IsPunctuation(c))
                 return "englishPunctuation";
diff --git a/WanaKanaShaapu/Node.cs b/WanaKanaShaapu/Node.cs
index d6bc8e6..2ea52e5 100644
--- a/WanaKanaShaapu/Node.cs
+++ b/WanaKanaShaapu/Node.cs
@@ -10,7 +10,7 @@ namespace WanaKanaShaapu
     public class Node
     {
         public string Data { get; set; } = string.Empty;
-        public Dictionary<string, Node> Children { get; set; } = new();
+        public Dictionary<string, Node> Children { get; set; } = new Dictionary<string, Node>();
 
         public Node FindChild(string key)
         {
diff --git a/WanaKanaShaapu/Tokenization.cs b/WanaKanaShaapu/Tokenization.cs
index 6be1cc6..33956a9 100644
--- a/WanaKanaShaapu/Tokenization.cs
+++ b/WanaKanaShaapu/Tokenization.cs
@@ -1,4 +1,6 @@
-using WanaKanaShaapu;
+using System.Collections.Generic;
+using System.Linq;
+using WanaKanaShaapu;
 
 namespace WanaKanaShaapu
 {
diff --git a/WanaKanaShaapu/TreeBuilder.cs b/WanaKanaShaapu/TreeBuilder.cs
index 81adf90..357b149 100644
--- a/WanaKanaShaapu/TreeBuilder.cs
+++ b/WanaKanaShaapu/TreeBuilder.cs
@@ -1,4 +1,6 @@
 
+using System.Collections.Generic;
+using System.Linq;
 using System.Text.Json;
 
 namespace WanaKanaShaapu
diff --git a/WanaKanaShaapu/TreeConstants.cs b/WanaKanaShaapu/TreeConstants.cs
index 98d3600..da9d3b3 100644
--- a/WanaKanaShaapu/TreeConstants.cs
+++ b/WanaKanaShaapu/TreeConstants.cs
@@ -1,4 +1,6 @@
-namespace WanaKanaShaapu
+using System.Collections.Generic;
+
+namespace WanaKanaShaapu
 {
     public static class TreeConstants
     {
diff --git a/WanaKanaShaapu/TreeTraverser.cs b/WanaKanaShaapu/TreeTraverser.cs
index 661712f..fa34976 100644
--- a/WanaKanaShaapu/TreeTraverser.cs
+++ b/WanaKanaShaapu/TreeTraverser.cs
@@ -1,4 +1,6 @@
-using System.Runtime.InteropServices;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
 
 namespace WanaKanaShaapu
 {
diff --git a/WanaKanaShaapu/WanaKana.cs b/WanaKanaShaapu/WanaKana.cs
index 6be6593..8d6c442 100644
--- a/WanaKanaShaapu/WanaKana.cs
+++ b/WanaKanaShaapu/WanaKana.cs
@@ -1,4 +1,6 @@
-using System.Runtime.InteropServices;
+using System;
+using System.Linq;
+using System.Runtime.InteropServices;
 using System.Text.RegularExpressions;
 using WanaKanaShaapu;
 using WanaKanaShaapu.Internal;
diff --git a/WanaKanaShaapu/WanaKanaShaapu.csproj b/WanaKanaShaapu/WanaKanaShaapu.csproj
index 84b164a..eeaeadc 100644
--- a/WanaKanaShaapu/WanaKanaShaapu.csproj
+++ b/WanaKanaShaapu/WanaKanaShaapu.csproj
@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
+    <TargetFramework>netstandard2.1</TargetFramework>
+    <ImplicitUsings>disable</ImplicitUsings>
     <Nullable>disable</Nullable>
     <Company />
     <Authors>kmoroz</Authors>
@@ -18,6 +18,10 @@
     <EmbeddedResource Include="wanikanilogo.png" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="System.Text.Json" Version="8.0.4" />
+  </ItemGroup>
+
   <ItemGroup>
     <None Update="wanikanilogo.png">
       <Pack>True</Pack>