diff --git a/generators/fireworks.py b/generators/fireworks.py
index ddb5048..8a7fa62 100755
--- a/generators/fireworks.py
+++ b/generators/fireworks.py
@@ -71,9 +71,20 @@ class Rocket:
 def getRandomColor(maxval):
     return list(map(lambda x: int(round(x*maxval)), colorsys.hsv_to_rgb(random.random(), 1, 1)))
 
+def gen_rockets(num, now=0):
+    for i in range(num):
+        yield Rocket(
+            np.array([random.randint(0, dim.width-1), dim.height-1]),
+            np.array([random.randint(-8, 8), -20 + random.randint(-2, 2)]),
+            4 + random.randint(-2, 2),
+            now + random.randint(0, 40) / 10,
+            np.array([dim.depth-1] * 3)
+        )
+
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Generate plasma animations')
     parser.add_argument('-d', '--delay', type=int, default=50)
+    parser.add_argument('-t', '--time', type=int, default=0)
     parser.add_argument('-n', '--num-rockets', type=int, default=3)
     parser.add_argument('output_file')
     args = parser.parse_args()
@@ -82,17 +93,7 @@ if __name__ == '__main__':
     anim = blup.animation.Animation(dim)
     anim.tags['description'] = ' '.join(sys.argv)
 
-    rockets = []
-    for i in range(args.num_rockets):
-        rockets.append(
-            Rocket(
-                np.array([random.randint(0, dim.width-1), dim.height-1]),
-                np.array([random.randint(-8, 8), -20 + random.randint(-2, 2)]),
-                4 + random.randint(-2, 2),
-                random.randint(0, 40) / 10,
-                np.array([dim.depth-1] * 3)
-            )
-        )
+    rockets = list(gen_rockets(args.num_rockets))
 
     fbs = []
     t = 0
@@ -126,7 +127,12 @@ if __name__ == '__main__':
         anim.addFrame(frame)
 
         if len(rockets) == 0 and len(fbs) == 0:
-            break
+            if t < args.time:
+                frame = blup.animation.AnimationFrame(dim, 700)
+                anim.addFrame(frame)
+                rockets = list(gen_rockets(args.num_rockets, t))
+            else:
+                break
         t += args.delay / 1000
 
     blup.writebml.writeBml(anim, args.output_file)