diff --git a/main.lua b/main.lua
index 074fc34..f200bed 100644
--- a/main.lua
+++ b/main.lua
@@ -1,48 +1,59 @@
 oop = require("oop/oop")
 
-function Vault(cls)
-    cls.setattr(cls, "public_note", nil, "public")
-    cls.setattr(cls, "protected_note", nil, "protected")
-    cls.setattr(cls, "private_note", nil, "private")
+function BankAccount(cls)
+    cls.setattr(cls, "owner", nil, cls.visibility.PUBLIC)
+    cls.setattr(cls, "balance", nil, cls.visibility.PUBLIC)
+    cls.setattr(cls, "pin", nil, cls.visibility.PROTECTED)
+    cls.setattr(cls, "token", nil, cls.visibility.PRIVATE)
 
-    cls.method("public_method", function(this)
-        print("public_method:", this.public_note)
-    end, "public")
+    cls.method("deposit", function(this, amount)
+        this.balance = this.balance + amount
+        print("deposit:", amount, "balance:", this.balance)
+    end, cls.visibility.PUBLIC)
 
-    cls.method("protected_method", function(this)
-        print("protected_method:", this.protected_note)
-    end, "protected")
+    cls.method("withdraw", function(this, amount, pin)
+        if pin ~= this.pin then
+            print("bad pin")
+            return
+        end
+        this.balance = this.balance - amount
+        print("withdraw:", amount, "balance:", this.balance)
+    end, cls.visibility.PUBLIC)
 
-    cls.method("private_method", function(this)
-        print("private_method:", this.private_note)
-    end, "private")
+    cls.method("audit", function(this)
+        print("audit:", this.owner, "balance:", this.balance)
+    end, cls.visibility.PROTECTED)
 
-    function cls.__init(this)
-        this.public_note = "hello"
-        this.protected_note = "shielded"
-        this.private_note = "secret"
+    cls.method("rotate_token", function(this)
+        this.token = "t-" .. tostring(os.time())
+        print("token rotated")
+    end, cls.visibility.PRIVATE)
+
+    function cls.__init(this, owner, pin)
+        this.owner = owner
+        this.balance = 0
+        this.pin = pin
+        this.token = "t-" .. tostring(os.time())
     end
 end
 
-function SubVault(cls)
-    cls.inherit(Vault)
+function PremiumAccount(cls)
+    cls.inherit(BankAccount)
 
-    function cls.show_all(this)
-        print("inside SubVault:")
-        this.public_method()
-        this.protected_method()
-        this.private_method()
+    function cls.monthly_bonus(this)
+        this.deposit(25)
+        this.audit()
     end
 end
 
-local v = oop.new(Vault)
-print("outside Vault:")
-print("public_note:", v.public_note)
-v.public_method()
-print("protected_note:", v.protected_note)
-print("private_note:", v.private_note)
-v.protected_method()
-v.private_method()
+local acct = oop.new(BankAccount, "Kim", 1234)
+acct.deposit(100)
+acct.withdraw(30, 1234)
 
-local s = oop.new(SubVault)
-s.show_all()
+local vip = oop.new(PremiumAccount, "Sam", 9999)
+vip.monthly_bonus()
+
+local ok, err = pcall(function()
+    vip.rotate_token()
+end)
+print("rotate_token from outside:", ok, err)