diff --git a/lib/fibonacci.rb b/lib/fibonacci.rb
index 7465c25..4f717cb 100644
--- a/lib/fibonacci.rb
+++ b/lib/fibonacci.rb
@@ -1,8 +1,13 @@
 # Improved Fibonacci
 
-# Time Complexity - ?
-# Space Complexity - ?  (should be O(n))
+# Time Complexity - o(n)
+# Space Complexity - o(n)  (should be O(n))
 # Hint, you may want a recursive helper method
 def fibonacci(n)
- 
+    # base case: n = 0 => 0, n = 1 => 1
+    return raise ArgumentError if n < 0
+    return n if n == 0 || n == 1
+
+    # recursive case
+    return fibonacci(n - 2) + fibonacci(n - 1) # return fib(6) + fib(7) => 8 + 13 => 21
 end
diff --git a/lib/super_digit.rb b/lib/super_digit.rb
index 33e367f..658c462 100644
--- a/lib/super_digit.rb
+++ b/lib/super_digit.rb
@@ -1,9 +1,10 @@
 # Superdigit
 
-# Time Complexity - ?
-# Space Complexity - ?
+# Time Complexity - o(n)
+# Space Complexity - o(n^2)
 def super_digit(n)
-   
+    return n if n < 10
+    return super_digit(n.digits.sum)
 end