diff --git a/fill3/fill3/__init__.py b/fill3/fill3/__init__.py
index 99f0eef..934c3b4 100755
--- a/fill3/fill3/__init__.py
+++ b/fill3/fill3/__init__.py
@@ -4,6 +4,7 @@
 
 import asyncio
 import contextlib
+import enum
 import itertools
 import os
 import re
@@ -192,16 +193,24 @@ class ScrollBar:
         return [bar] if self._is_horizontal else [char for char in bar]
 
 
+class Alignment(enum.Enum):
+    left = enum.auto()
+    right = enum.auto()
+    top = enum.auto()
+    bottom = enum.auto()
+    center = enum.auto()
+
+
 class Portal:
 
     def __init__(self, widget, position=(0, 0), background_char=" ",
-                 is_scroll_limited=False, is_left_aligned=True, is_top_aligned=True):
+                 is_scroll_limited=False, x_alignment=Alignment.left, y_alignment=Alignment.top):
         self.widget = widget
         self.position = position
         self.background_char = background_char
         self.is_scroll_limited = is_scroll_limited
-        self.is_left_aligned = is_left_aligned
-        self.is_top_aligned = is_top_aligned
+        self.x_alignment = x_alignment
+        self.y_alignment = y_alignment
         self.last_dimensions = 0, 0
 
     def _scroll_half_pages(self, dx, dy):
@@ -226,13 +235,27 @@ class Portal:
         widget_width, widget_height = appearance_dimensions
         x, y = self.position
         if widget_width <= portal_width:
-            x = 0 if self.is_left_aligned else (widget_width - portal_width)
+            if self.x_alignment == Alignment.left:
+                x = 0
+            elif self.x_alignment == Alignment.center:
+                x = (widget_width - portal_width) // 2
+            elif self.x_alignment == Alignment.right:
+                x = widget_width - portal_width
+            else:
+                raise NotImplementedError
         elif x < 0:
             x = 0
         elif x > (widget_width - portal_width):
             x = widget_width - portal_width
         if widget_height <= portal_height:
-            y = 0 if self.is_top_aligned else (widget_height - portal_height)
+            if self.y_alignment == Alignment.top:
+                y = 0
+            elif self.y_alignment == Alignment.center:
+                y = (widget_height - portal_height) // 2
+            elif self.y_alignment == Alignment.bottom:
+                y = widget_height - portal_height
+            else:
+                raise NotImplementedError
         elif y < 0:
             y = 0
         elif y > (widget_height - portal_height):
diff --git a/fill3/tests/fill3_test.py b/fill3/tests/fill3_test.py
index c375b49..28d4594 100755
--- a/fill3/tests/fill3_test.py
+++ b/fill3/tests/fill3_test.py
@@ -57,7 +57,7 @@ class WidgetTests(unittest.TestCase):
         portal.position = (1, 0)
         portal.limit_scroll((6, 1), (1, 1))
         self.assertEqual(portal.position, (0, 0))
-        portal.is_left_aligned = False
+        portal.x_alignment = fill3.Alignment.right
         portal.limit_scroll((6, 1), (1, 1))
         self.assertEqual(portal.position, (-5, 0))