--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nagslang/enemies.py	Tue Sep 03 14:39:38 2013 +0200
@@ -0,0 +1,116 @@
+import pymunk
+import pymunk.pygame_util
+
+from nagslang.constants import COLLISION_TYPE_ENEMY, ZORDER_MID
+from nagslang.game_object import (
+    GameObject, SingleShapePhysicser, AnimatedFacingImageRenderer, make_body)
+from nagslang.mutators import FLIP_H
+from nagslang.resources import resources
+
+
+class Enemy(GameObject):
+    """A base class for mobile enemies"""
+
+    def __init__(self, space, position):
+        self._setup_physics(space, position)
+        self._setup_renderer()
+
+        super(Enemy, self).__init__(
+            self._physicser, self.renderer)
+        self.zorder = ZORDER_MID
+
+    def _get_image(self, name, *transforms):
+        return resources.get_image('creatures', name, transforms=transforms)
+
+    def _setup_physics(self, space, position):
+        raise NotImplementedError
+
+    def _setup_renderer(self):
+        raise NotImplementedError
+
+    def attack(self):
+        raise NotImplementedError
+
+
+class PatrollingAlien(Enemy):
+
+    def __init__(self, space, position, end_position):
+        # An enemy that patrols between the two points
+        super(PatrollingAlien, self).__init__(space, position)
+        self._start_pos = position
+        self._end_pos = end_position
+        self._direction = 'away'
+
+    def _setup_physics(self, space, position):
+        self._body = make_body(5, pymunk.inf, position, 0.8)
+
+        self._shape = pymunk.Circle(self._body, 30)
+
+        self._shape.elasticity = 1.0
+        self._shape.friction = 10.0
+        self._shape.collision_type = COLLISION_TYPE_ENEMY
+        self._physicser = SingleShapePhysicser(space, self._shape)
+        self.impulse_factor = 50
+        self.angle = 0
+
+    def _setup_renderer(self):
+        self.renderer = AnimatedFacingImageRenderer(
+            (self._get_image('alien_A_1.png'),
+             self._get_image('alien_A_1.png'),
+             self._get_image('alien_A_1.png'),
+             self._get_image('alien_A_1.png'),
+             self._get_image('alien_A_1.png'),
+             self._get_image('alien_A_1.png'),
+             self._get_image('alien_A_2.png'),
+             self._get_image('alien_A_2.png'),
+             self._get_image('alien_A_2.png')),
+            (self._get_image('alien_A_1.png', FLIP_H),
+             self._get_image('alien_A_1.png', FLIP_H),
+             self._get_image('alien_A_1.png', FLIP_H),
+             self._get_image('alien_A_1.png', FLIP_H),
+             self._get_image('alien_A_1.png', FLIP_H),
+             self._get_image('alien_A_1.png', FLIP_H),
+             self._get_image('alien_A_2.png', FLIP_H),
+             self._get_image('alien_A_2.png', FLIP_H),
+             self._get_image('alien_A_2.png', FLIP_H)))
+        # We're always animated
+        self.renderer.start()
+
+    def get_render_angle(self):
+        return self.angle
+
+    def _switch_direction(self):
+        if self._direction == 'away':
+            self._direction = 'towards'
+        else:
+            self._direction = 'away'
+
+    def set_direction(self, dx, dy):
+        self.angle = pymunk.Vec2d((dx, dy)).angle
+        self._body.apply_impulse(
+            (dx * self.impulse_factor, dy * self.impulse_factor))
+
+    def animate(self):
+        # Calculate the step every frame
+        if self._direction == 'away':
+            target = self._end_pos
+        else:
+            target = self._start_pos
+        x_step = 0
+        y_step = 0
+        if (target[0] < self._body.position[0]):
+            x_step = max(-1, target[0] - self._body.position[0])
+        elif (target[0] > self._body.position[0]):
+            x_step = min(1, target[0] - self._body.position[0])
+        if abs(x_step) < 0.5:
+            x_step = 0
+        if (target[1] < self._body.position[1]):
+            y_step = max(-1, target[1] - self._body.position[1])
+        elif (target[1] > self._body.position[1]):
+            y_step = min(1, target[1] - self._body.position[1])
+        if abs(y_step) < 0.5:
+            y_step = 0
+        if abs(x_step) < 1 and abs(y_step) < 1:
+            self._switch_direction()
+        self.set_direction(x_step, y_step)
+        super(PatrollingAlien, self).animate()