diff --git a/src/main/java/com/booleanuk/Scrabble.java b/src/main/java/com/booleanuk/Scrabble.java
index 88108a8..2ea38ec 100644
--- a/src/main/java/com/booleanuk/Scrabble.java
+++ b/src/main/java/com/booleanuk/Scrabble.java
@@ -1,12 +1,115 @@
 package com.booleanuk;
 
+import java.util.HashMap;
+import java.util.Stack;
+
 public class Scrabble {
-    public Scrabble(String word) {
+    private HashMap<Character, Integer> letterValues = new HashMap<>();
+    private String word;
 
+    public Scrabble(String word) {
+        this.word = word.toLowerCase().strip();
+        // add letter values
+        addLetters("aeioulnrst", 1);
+        addLetters("dg", 2);
+        addLetters("bcmp", 3);
+        addLetters("fhvwy", 4);
+        addLetters("k", 5);
+        addLetters("jx", 8);
+        addLetters("qz", 10);
     }
 
     public int score() {
-        return -1;
+        int score = 0;
+        Stack<Character> openBrackets = new Stack<>();
+
+        if (!isValid())
+            return 0;
+
+        for (char letter : word.toCharArray()) {
+            // add open brackets to stack
+            if (letter == '{' || letter == '[') {
+                openBrackets.add(letter);
+            } else if (letter == '}' || letter == ']') {
+                openBrackets.pop();
+            }
+
+            // add letter score with multiplier
+            if (letterValues.containsKey(letter)) {
+                score += letterValues.get(letter) * calculateMultiplier(openBrackets);
+            }
+        }
+
+        return score;
+    }
+
+    private int calculateMultiplier(Stack<Character> openBrackets) {
+        int multiplier = 1;
+        for (Character c : openBrackets) {
+            if (c == '{')
+                multiplier *= 2;
+            else if (c == '[')
+                multiplier *= 3;
+        }
+
+        return multiplier;
+    }
+
+    private boolean isValid() {
+        Stack<Character> brackets = new Stack<>();
+
+        int totalLetters = 0;
+        int lettersInBrackets = 0;
+
+        for (Character c : word.toCharArray()) {
+            // check if invalid character
+            if (!letterValues.containsKey(c) && c != '{' && c != '}' && c != '[' && c != ']') {
+                return false;
+            }
+
+            // add open brackets to stack
+            if (c == '{' || c == '[') {
+                brackets.add(c);
+            }
+            // check for matching open bracket if this is a closing bracket
+            else if (c == '}' || c == ']') {
+                if (brackets.isEmpty())
+                    return false;
+                
+                // if found match, pop from stack
+                if ((c == '}' && brackets.peek() == '{') || (c == ']' && brackets.peek() == '[')) {
+                    brackets.pop();
+
+                    // return false if brackets contain more than one letter and is not a word multiplier
+                    if (lettersInBrackets > 1 && lettersInBrackets < totalLetters)
+                        return false;
+
+                    totalLetters -= lettersInBrackets;
+                    lettersInBrackets = 0;
+                } else {
+                    return false;
+                }
+            } else {
+                // c is a letter
+                totalLetters += 1;
+
+                if (!brackets.isEmpty()) {
+                    lettersInBrackets += 1;
+                }
+            }
+        }
+
+        // if open brackets were not closed
+        if (!brackets.isEmpty())
+            return false;
+
+        return true;
+    }
+
+    private void addLetters(String letters, int value) {
+        for (char letter : letters.toCharArray()) {
+            letterValues.put(letter, value);
+        }
     }
 
 }