added astroids and astroid field

asteroid.py

@@ -0,0 +1,16 @@
+import circleshape
+import pygame
+import constants
+
+class Asteroid(circleshape.CircleShape):
+    
+    containers = []
+
+    def __init__(self, x, y, radius):
+         super().__init__(x,y,radius)
+
+    def draw(self,screen):
+        pygame.draw.circle(screen,(255,255,255),self.position,self.radius,2)
+
+    def update(self, dt):
+        self.position += self.velocity * dt