diff --git a/assets/css/app.less b/assets/css/app.less
index 24ed8a2..d1c9f1d 100644
--- a/assets/css/app.less
+++ b/assets/css/app.less
@@ -21,9 +21,7 @@ body {
 }
 
 .command {
-  border-width: 2px 0 0 0;
-  border-style: solid;
-  border-color: gray;
+  border-top: 2px solid @gray;
   form {
     margin: 0;
     .prompt {
diff --git a/assets/js/view_models/client.coffee b/assets/js/view_models/client.coffee
index aac9034..78a8782 100644
--- a/assets/js/view_models/client.coffee
+++ b/assets/js/view_models/client.coffee
@@ -87,7 +87,7 @@ class ClientView
   setSizes: ->
     inputWidthDiff = @input.outerWidth() - @input.width()
     @input.width($('.ui-layout-center').width() - inputWidthDiff - $('.prompt').outerWidth())
-    @screen.height($('.ui-layout-center').height() - @input.outerHeight())
+    @screen.height($('.ui-layout-center').height() - @input.outerHeight() - 2)
 
     # if an ace editor is present, call it's resize function
     # and set sizes for all the form elements to make them look prettier
diff --git a/lib/context.coffee b/lib/context.coffee
index 624872c..f9cdde7 100644
--- a/lib/context.coffee
+++ b/lib/context.coffee
@@ -50,6 +50,11 @@ class Context
         x
 
   serialize: (x) =>
+    try
+      JSON.stringify x
+    catch error
+      throw new Error 'Unserializable property'
+
     switch typeof x
       when 'object'
         if x == null
diff --git a/lib/object.coffee b/lib/object.coffee
index 3e7bd78..d23fc95 100644
--- a/lib/object.coffee
+++ b/lib/object.coffee
@@ -72,6 +72,8 @@ exports.RoomJsObject = class
       true
     else
       object = @db.findById id
+      if object.inheritsFrom @id
+        throw new Error 'Cannot create circular inheritance'
       if not object?
         throw new Error "Invalid object"
       @parent_id = id