diff --git a/lib/desugaring.rb b/lib/desugaring.rb
index 8d52908..8965330 100644
--- a/lib/desugaring.rb
+++ b/lib/desugaring.rb
@@ -21,7 +21,9 @@ def all_the_sugar(recipients, event, message)
   # Copy the contents of the previous method here and remove this sugar.
   #
   def desugared_poetry(recipients, event, message)
-    implement_me!
+    mail(message,
+         to: recipients.map(&:email),
+         subject: "You’re invited to #{event.title} on #{event.date}")
   end
 
   # Ruby allows you to pass arguments identified by name instead of just by position. They are really just
@@ -36,7 +38,9 @@ def desugared_poetry(recipients, event, message)
   # Copy the contents of the previous method here and remove this sugar.
   #
   def desugared_named_args(recipients, event, message)
-    implement_me!
+    mail(message,
+         {to: recipients.map(&:email),
+          subject: "You’re invited to #{event.title} on #{event.date}"})
   end
 
   # Ruby’s general syntax for hashes is `{key => value, key => value, ...}`. Because it is so common to use
@@ -51,7 +55,9 @@ def desugared_named_args(recipients, event, message)
   # Copy the contents of the previous method here and remove this sugar.
   #
   def desugared_symbol_keys(recipients, event, message)
-    implement_me!
+    mail(message,
+         {:to => recipients.map(&:email),
+          :subject => "You’re invited to #{event.title} on #{event.date}"})
   end
 
   # You may be wondering how `map(&:email)` works. When you precede the last argument of a method call with
@@ -70,7 +76,9 @@ def desugared_symbol_keys(recipients, event, message)
   # Copy the contents of the previous method here and remove this sugar.
   #
   def desugared_attr_proc(recipients, event, message)
-    implement_me!
+    mail(message,
+         {:to => recipients.map{|x| x.email},
+          :subject => "You’re invited to #{event.title} on #{event.date}"})
   end
 
   # You may recall from the Ruby koans that when you put `#{something}` in a `"`-delimited string, Ruby will
@@ -88,7 +96,9 @@ def desugared_attr_proc(recipients, event, message)
   # Copy the contents of the previous method here and remove this sugar.
   #
   def desugared_interpolation(recipients, event, message)
-    implement_me!
+    mail(message,
+         {:to => recipients.map{|x| x.email},
+          :subject => "You’re invited to " + event.title + " on " + event.date})
   end
 
   # Ruby tracks local variables lexically at compile time. Wherever you say `x = y`, the compiler assumes that
@@ -110,7 +120,10 @@ def desugared_interpolation(recipients, event, message)
   # (Think: which names are local variables, and which are not?)
   #
   def desugared_implicit_self(recipients, event, message)
-    implement_me!
+    # I had some trouble here because I instinctively kept writing this.mail() and wasn't sure why it wasn't working
+    self.mail(message,
+              {:to => recipients.map{|x| x.email},
+               :subject => "You’re invited to " + event.title + " on " + event.date})
   end
 
   # In Ruby, unlike Python, there are no properties distinct from method calls. When you say `x.y`, you are
@@ -131,7 +144,9 @@ def desugared_implicit_self(recipients, event, message)
   # but structurally quite similar!
   #
   def desugared_implicit_parens(recipients, event, message)
-    implement_me!
+    self.mail(message,
+              {:to => recipients.map{|x| x.email()},
+               :subject => "You’re invited to " + event.title() + " on " + event.date()})
   end
 
   # In Ruby, every value is an object and every action is a method call. That includes operators. A binary
@@ -153,7 +168,9 @@ def desugared_implicit_parens(recipients, event, message)
   #   get added before the things on the right. (a + b + c) means ((a + b) + c), NOT (a + (b + c)).
   #
   def desugared_operators(recipients, event, message)
-    implement_me!
+    self.mail(message,
+         {:to => recipients.map{|x| x.email()},
+          :subject => "You’re invited to ".+(event.title()).+(" on ").+(event.date())})
   end
 
   # Compare that to the version at the top.
diff --git a/lib/door.rb b/lib/door.rb
index 0f99a74..0ade1f4 100644
--- a/lib/door.rb
+++ b/lib/door.rb
@@ -16,29 +16,46 @@ class Door
     end
   end
 
-  aasm :deadbolt_lock, namespace: :deadbolt do
-    state :unlocked, initial: true
-    state :locked
-
-    event :lock_deadbolt do
-      transitions to: :locked
-    end
-
-    event :unlock_deadbolt do
-      transitions to: :unlocked
+  # I tried adding a method to do this to Class without success
+  # But this works too
+  ["deadbolt", "knob"].each do |name|
+    aasm "#{name}_lock".to_sym, namespace: name.to_sym do
+      state :unlocked, initial: true
+      state :locked
+
+      event "lock_#{name}".to_sym do
+        transitions to: :locked
+      end
+
+      event "unlock_#{name}".to_sym do
+        transitions to: :unlocked
+      end
     end
   end
 
-  aasm :knob_lock, namespace: :knob do
-    state :unlocked, initial: true
-    state :locked
-
-    event :lock_knob do
-      transitions to: :locked
-    end
-
-    event :unlock_knob do
-      transitions to: :unlocked
-    end
-  end
+  # aasm :deadbolt_lock, namespace: :deadbolt do
+  #   state :unlocked, initial: true
+  #   state :locked
+  #
+  #   event :lock_deadbolt do
+  #     transitions to: :locked
+  #   end
+  #
+  #   event :unlock_deadbolt do
+  #     transitions to: :unlocked
+  #   end
+  # end
+  #
+  # aasm :knob_lock, namespace: :knob do
+  #   state :unlocked, initial: true
+  #   state :locked
+  #
+  #   event :lock_knob do
+  #     transitions to: :locked
+  #   end
+  #
+  #   event :unlock_knob do
+  #     transitions to: :unlocked
+  #   end
+  # end
 end
diff --git a/lib/retail_transaction.rb b/lib/retail_transaction.rb
index 1bfa0e3..5bb48d6 100644
--- a/lib/retail_transaction.rb
+++ b/lib/retail_transaction.rb
@@ -39,6 +39,11 @@ def paid?
     state :processing_payment
     state :payment_declined
     state :settled
+    state :refunded
+
+    event :refund do
+      transitions from: :settled, to: :refunded
+    end
 
     event :check_out do
       transitions from: :ringing_up, to: :collecting_payment,
diff --git a/test/retail_transaction_test.rb b/test/retail_transaction_test.rb
index 823cbfe..a1aa84c 100644
--- a/test/retail_transaction_test.rb
+++ b/test/retail_transaction_test.rb
@@ -103,6 +103,12 @@
       assert_equal false, tx.settled?
       assert_equal true,  tx.payment_declined?
     end
+
+    it "cannot be refunded yet" do
+      assert_raises do
+        tx.refund!
+      end
+    end
   end
 
   describe "with declined payment" do
@@ -138,6 +144,12 @@
       assert_equal false, tx.payment_declined?
       assert_equal true,  tx.processing_payment?
     end
+
+    it "cannot be refunded yet" do
+      assert_raises do
+        tx.refund!
+      end
+    end
   end
 
   describe "that is settled" do
@@ -152,5 +164,40 @@
     it "cannot be reopened" do
       assert_invalid_transition { tx.reopen! }
     end
+
+    it "can be refunded" do
+      tx.refund!
+      assert_equal false, tx.settled?
+      assert_equal true, tx.refunded?
+    end
+  end
+
+  describe "after refund" do
+    before(:each) do
+      tx.add_item("12lb bag of gummy bears")
+      tx.check_out!
+      tx.payment_info = "Laundry fund"
+      tx.process_payment!
+      tx.payment_authorized!
+      tx.refund!
+    end
+
+    it "doesn't accept new payment info" do
+      assert_raises do
+        tx.payment_info = "Snax Account"
+      end
+    end
+
+    it "can't be resubmitted" do
+      assert_raises do
+        tx.process_payment!
+      end
+    end
+
+    it "can't be refunded again" do
+      assert_raises do
+        tx.refund!
+      end
+    end
   end
 end