diff --git a/csharp-scrabble-challenge.Main/Program.cs b/csharp-scrabble-challenge.Main/Program.cs
index 3751555..3791da9 100644
--- a/csharp-scrabble-challenge.Main/Program.cs
+++ b/csharp-scrabble-challenge.Main/Program.cs
@@ -1,2 +1,10 @@
 // See https://aka.ms/new-console-template for more information
+using csharp_scrabble_challenge.Main;
+using System.IO;
+
 Console.WriteLine("Hello, World!");
+
+Scrabble s = new Scrabble("[h}ous{e}]");
+var score = s.score();
+
+Console.WriteLine($"score = {score}");
\ No newline at end of file
diff --git a/csharp-scrabble-challenge.Main/Scrabble.cs b/csharp-scrabble-challenge.Main/Scrabble.cs
index c1ea013..bfc480e 100644
--- a/csharp-scrabble-challenge.Main/Scrabble.cs
+++ b/csharp-scrabble-challenge.Main/Scrabble.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection.Metadata.Ecma335;
+using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading.Tasks;
 
@@ -9,15 +10,118 @@ namespace csharp_scrabble_challenge.Main
 {
     public class Scrabble
     {
+        private Dictionary<char, int> letterToScoreMap = new()
+        {
+            {'a', 1},
+            {'b', 3},
+            {'c', 3},
+            {'d', 2},
+            {'e', 1},
+            {'f', 4},
+            {'g', 2},
+            {'h', 4},
+            {'i', 1},
+            {'j', 8},
+            {'k', 5},
+            {'l', 1},
+            {'m', 3},
+            {'n', 1},
+            {'o', 1},
+            {'p', 3},
+            {'q', 10},
+            {'r', 1},
+            {'s', 1},
+            {'t', 1},
+            {'u', 1},
+            {'v', 4},
+            {'w', 4},
+            {'x', 8},
+            {'y', 4},
+            {'z', 10}
+        };
+
+        private string processedWord;
+
+        // [] triple points
+        // {} double points
+
+        private const char startDoublePoints = '{';
+        private const char endDoublePoints = '}';
+
+        private const char startTriplePoints = '[';
+        private const char endTriplePoints = ']';
+
+        bool isDoublePointsActive = false;
+        bool isTriplePointsActive = false;
+
+        int doublePointsMultiplier = 2;
+        int triplePointsMultiplier = 3;
+
+        bool endedBonusBeforeStarting = false;
+
         public Scrabble(string word)
-        {            
-            //TODO: do something with the word variable
+        {
+            processedWord = word.ToLowerInvariant();
         }
 
         public int score()
         {
-            //TODO: score calculation code goes here
-            throw new NotImplementedException(); //TODO: Remove this line when the code has been written
+            int totalScore = 0;
+
+            foreach (var letter in processedWord)
+            {
+
+                switch (letter)
+                {
+                    case startDoublePoints:
+                        isDoublePointsActive = true;
+                        break;
+
+                    case endDoublePoints:
+                        if(!isDoublePointsActive)
+                            endedBonusBeforeStarting = true;
+
+                        isDoublePointsActive = false; 
+                        break;
+
+                    case startTriplePoints:
+                        isTriplePointsActive = true;
+                        break;
+
+                    case endTriplePoints:
+                        if (isTriplePointsActive == false)
+                            endedBonusBeforeStarting = true;
+
+                        isTriplePointsActive = false;
+                        break;
+
+                    default:
+                        bool isValid = char.IsLetter(letter);
+                        if (!isValid)
+                            return 0;
+                        
+                        break;
+                }
+
+                letterToScoreMap.TryGetValue(letter, out var score);
+
+                if (isDoublePointsActive)
+                    score *= doublePointsMultiplier;
+                    
+                if (isTriplePointsActive)
+                    score *= triplePointsMultiplier;
+                    
+
+                totalScore += score;
+            }
+
+            if (isDoublePointsActive || isTriplePointsActive)
+                return 0;
+
+            if (endedBonusBeforeStarting)
+                return 0;
+
+            return totalScore;
         }
     }
 }
diff --git a/csharp-scrabble-challenge.Test/ExtensionTests.cs b/csharp-scrabble-challenge.Test/ExtensionTests.cs
index 8eb37dc..07dcbac 100644
--- a/csharp-scrabble-challenge.Test/ExtensionTests.cs
+++ b/csharp-scrabble-challenge.Test/ExtensionTests.cs
@@ -14,10 +14,28 @@ public class ExtensionTests
 
         [TestCase("{street}", 12)] //extension double word
         [TestCase("[street]", 18)] //extension triple word
+        [TestCase("{s}treet", 7)] //extension double word
+        [TestCase("[st]reet", 10)] //extension triple word
+        [TestCase("[st]ree{t}", 11)] //extension triple word
+        [TestCase("[st}ree[t}", 0)] //extension triple word
         [TestCase("{quirky}", 44)] //extension double word
         [TestCase("[quirky]", 66)] //extension triple word
         [TestCase("{OXyPHEnBUTaZoNE}", 82)]
         [TestCase("[OXyPHEnBUTaZoNE]", 123)]
+        [TestCase("[{h}o1s{e}]", 0)] // error case (zero for errors)
+        [TestCase("{h}ous{e}", 13)]
+        [TestCase("[{h}ous{e}]", 39)]
+        [TestCase("[h}ous{e}]", 0)] //Error case (zero for errors)
+        [TestCase("", 0)]
+        [TestCase(" ", 0)]
+        [TestCase(" \t\n", 0)]
+        [TestCase("\n\r\t\b\f", 0)]
+        [TestCase("a", 1)]
+        [TestCase("f", 4)]
+        [TestCase("OXyPHEnBUTaZoNE", 41)]
+        [TestCase("quirky", 22)]
+        [TestCase("street", 6)]
+        [TestCase("]street[", 0)]
         public void ExtendedCriteriaTests(string word, int targetScore)
         {
             Assert.AreEqual(this.GetWordScore(word), targetScore);