--- a/nagslang/enemies.py	Thu Sep 05 00:08:58 2013 +0200
+++ b/nagslang/enemies.py	Thu Sep 05 00:05:17 2013 +0200
@@ -126,6 +126,9 @@
         self.set_direction(x_step, y_step)
         super(PatrollingAlien, self).animate()
 
+    def collide_with_protagonist(self):
+        return 5
+
     @classmethod
     def requires(cls):
         return [("name", "string"), ("position", "coordinates"),

--- a/nagslang/screens/area.py	Thu Sep 05 00:08:58 2013 +0200
+++ b/nagslang/screens/area.py	Thu Sep 05 00:05:17 2013 +0200
@@ -4,7 +4,8 @@
 import pymunk
 import pymunk.pygame_util
 
-from nagslang.constants import COLLISION_TYPE_PLAYER, CALLBACK_COLLIDERS
+from nagslang.constants import COLLISION_TYPE_PLAYER, CALLBACK_COLLIDERS, \
+    COLLISION_TYPE_ENEMY
 from nagslang.events import ScreenChange, DoorEvent
 from nagslang.level import Level
 from nagslang.protagonist import Protagonist
@@ -84,6 +85,8 @@
     def _collision_pre_solve_handler(self, space, arbiter):
         gobj = arbiter.shapes[1].physicser.game_object
         result = gobj.collide_with_protagonist(self.protagonist)
+        if arbiter.shapes[1].collision_type == COLLISION_TYPE_ENEMY:
+            self.protagonist.lose_health(15)
         # The collision handler must return `True` or `False`. We don't want to
         # accidentally reject collisions from handlers that return `None`, so
         # we explicitly check for `False` and treate everything else as `True`.
@@ -189,8 +192,12 @@
 
         super(AreaScreen, self).tick(seconds)
 
-    def render_health_bar(self, surface):
+    def render_health_bar(self, surface, damage_experienced=None):
         rect = pygame.Rect(50, 500, 110, 50)
+        if damage_experienced:
+            health_box_colour = pygame.color.THECOLORS['red']
+        else:
+            health_box_colour = pygame.color.THECOLORS['white']
         pygame.draw.rect(surface,  health_box_colour, rect, 0)
         if self.protagonist.in_human_form():
             health_colour = pygame.color.THECOLORS['red']