diff --git a/lib/fibonacci.rb b/lib/fibonacci.rb
index 7465c25..a20bd75 100644
--- a/lib/fibonacci.rb
+++ b/lib/fibonacci.rb
@@ -1,8 +1,29 @@
 # Improved Fibonacci
 
-# Time Complexity - ?
+# Time Complexity - o(n)
 # Space Complexity - ?  (should be O(n))
 # Hint, you may want a recursive helper method
 def fibonacci(n)
- 
+  if n < 0
+    raise ArgumentError.new
+  end
+  return fib_helper([0, 1], 2, n)
+end
+
+def fib_helper(solutions, current, n)
+  if n == 0 || n == 1
+    return n
+  end
+  if current == n
+    return solutions[n - 1] + solutions[n - 2]
+  end
+
+  solutions.push(solutions[current - 1] + solutions[current - 2])
+  return fib_helper(solutions, current + 1, n)
+
+  #   puts fib(3)
+  #   puts fib(5)
+  #   puts fib(0)
+  #   puts fib(8)
+
 end
diff --git a/lib/super_digit.rb b/lib/super_digit.rb
index 33e367f..493fdd0 100644
--- a/lib/super_digit.rb
+++ b/lib/super_digit.rb
@@ -1,15 +1,15 @@
 # Superdigit
 
-# Time Complexity - ?
-# Space Complexity - ?
+# Time Complexity - O(n)
+# Space Complexity - O(n)
 def super_digit(n)
-   
+  if n < 10
+    return n
+  end
+  return super_digit(n.digits.sum)
 end
-  
 
 # Time Complexity - ?
 # Space Complexity - ?
 def refined_super_digit(n, k)
-    
 end
-    
\ No newline at end of file
diff --git a/test/super_digit_test.rb b/test/super_digit_test.rb
index 60da3a1..e811962 100644
--- a/test/super_digit_test.rb
+++ b/test/super_digit_test.rb
@@ -1,6 +1,6 @@
 require_relative "test_helper"
 
-xdescribe "super_digit" do
+describe "super_digit" do
   it "will return 2 for super_digit(9875)" do
     # Act
     answer = super_digit(9875)
@@ -15,7 +15,7 @@
 
     # Assert
     expect(answer).must_equal 5
-   end
+  end
 
   it "will return 6 for super_digit(123)" do
     # Act
@@ -33,13 +33,13 @@
     expect(answer).must_equal 6
   end
 
-  describe "refined superdigit" do 
+  describe "refined superdigit" do
     it "will return 1 for n = 1 and k = 1" do
       # Act
       answer = refined_super_digit(1, 1)
 
       # Assert
-      expect(answer).must_equal 1      
+      expect(answer).must_equal 1
     end
 
     it "will return 8 for n=9875 and k = 4" do
@@ -51,11 +51,11 @@
     end
 
     it "will return 3 for n=148 and k = 3" do
-        # Act
-        answer = refined_super_digit(148, 3)
-  
-        # Assert
-        expect(answer).must_equal 3
+      # Act
+      answer = refined_super_digit(148, 3)
+
+      # Assert
+      expect(answer).must_equal 3
     end
   end
 end