diff --git a/generators/unrath.py b/generators/unrath.py
index 9f38dfb..c8f96e1 100755
--- a/generators/unrath.py
+++ b/generators/unrath.py
@@ -29,20 +29,9 @@ def get_random_color():
     return colorsys.hsv_to_rgb(random.random(), s, v)
 
 
-def cap(x):
-    return min(1, max(0, x))
-
-
-def cyc(x):
-    while x < 0:
-        x += 1
-    while x > 1:
-        x -= 1
-    return x
-
-
 class Unrath:
-    def __init__(self):
+    def __init__(self, world):
+        self.world = world
         self.shape = set([(0, 0)])
         shapesize = random.randint(2, 5)
         while len(self.shape) < shapesize:
@@ -63,25 +52,59 @@ class Unrath:
         self.speed = d * random.randint(2, WIDTH/2)
         self.color = get_random_color()
 
-    def update(self, dt):
+    def update(self, dt, nocheck=False):
         if (self.pos[0] + self.shapewidth < 0 and self.speed < 0) or \
            (self.pos[0] > WIDTH and self.speed > 0):
            self.finished = True
-        else:
-            self.pos = (self.pos[0] + dt*self.speed, self.pos[1])
+           return
+        newpos = (self.pos[0] + dt*self.speed, self.pos[1])
+        newpoints = self.get_points(newpos)
+        collision = False
+        for unrath in self.world.unraethe - {self}:
+            if len(unrath.get_points().intersection(newpoints)) > 0:
+                collision = True
+                if abs(unrath.speed) > abs(self.speed):
+                    fast = unrath
+                    slow = self
+                else:
+                    slow = unrath
+                    fast = self
+                slow.speed = fast.speed * 1.1
+                slow.update(dt, True)
+        if not collision:
+            self.pos = newpos
+
+    def get_points(self, pos=None):
+        if pos is None:
+            pos = self.pos
+        return {(int(pos[0] + s[0]), int(pos[1] + s[1])) for s in self.shape}
 
     def draw(self, frame):
-        for p in self.shape:
+        for p in self.get_points():
             try:
-                frame.setPixel(
-                    int(self.pos[0] + p[0]),
-                    int(self.pos[1] + p[1]),
-                    convert_color(self.color)
-                )
+                frame.setPixel(p[0], p[1], convert_color(self.color))
             except ValueError:
                 pass
 
 
+class World:
+    def __init__(self, num_unraethe):
+        self.num_unraethe = num_unraethe
+        self.unraethe = {}
+
+    def update(self, dt):
+        self.unraethe = set(filter(lambda u: not u.finished, self.unraethe))
+        if len(self.unraethe) < self.num_unraethe:
+            self.unraethe.add(Unrath(self))
+
+        for u in self.unraethe:
+            u.update(dt)
+
+    def draw(self, frame):
+        for u in self.unraethe:
+            u.draw(frame)
+
+
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Generate Unrath animations')
     parser.add_argument('-d', '--delay', type=int, default=50)
@@ -95,19 +118,12 @@ if __name__ == '__main__':
     anim.tags['description'] = ' '.join(sys.argv)
 
     t = 0
-    unraethe = []
+    w = World(args.num_unraethe)
     while t < args.time:
         t += args.delay / 1000
         frame = blup.animation.AnimationFrame(dim, args.delay)
-
-        unraethe = list(filter(lambda u: not u.finished, unraethe))
-        if len(unraethe) < args.num_unraethe:
-            unraethe.append(Unrath())
-
-        for u in unraethe:
-            u.update(args.delay / 1000)
-            u.draw(frame)
-
+        w.update(args.delay / 1000)
+        w.draw(frame)
         anim.addFrame(frame)
 
     blup.writebml.writeBml(anim, args.output_file)