# HG changeset patch
# User Simon Cross <hodgestar@gmail.com>
# Date 1378050043 -7200
# Node ID 1d087f79ca2940213cc5991fd4eacb68d25b76ac
# Parent  5ef22357291a4ded117bc20437cda91a871cac1f
Use fixed timestemp because pymunk docs say this is an order of magnitude more efficient.

diff -r 5ef22357291a -r 1d087f79ca29 nagslang/engine.py
--- a/nagslang/engine.py	Sun Sep 01 17:40:30 2013 +0200
+++ b/nagslang/engine.py	Sun Sep 01 17:40:43 2013 +0200
@@ -13,6 +13,7 @@
         self._surface = surface
         self._clock = pygame.time.Clock()
         self._fps = constants.FPS
+        self._dt = 1. / self._fps
         self._world = None  # TODO: create the world
         self._current_screen = None
         self._screens = {
@@ -38,7 +39,7 @@
                     self.change_screen(ev.screen)
                 else:
                     self._current_screen.handle_event(ev)
+            self._current_screen.tick(self._dt)
             self._current_screen.render(self._surface)
             pygame.display.flip()
-            ms = self._clock.tick(self._fps)
-            self._current_screen.tick(ms / 1000.)
+            self._clock.tick(self._fps)