1 files changed, 51 insertions, 0 deletions
diff --git a/asteroidfield.py b/asteroidfield.py
new file mode 100644
index 0000000..da82d41
--- /dev/null
+++ b/asteroidfield.py
@@ -0,0 +1,51 @@
+import pygame
+import random
+from asteroid import Asteroid
+from constants import *
+
+
+class AsteroidField(pygame.sprite.Sprite):
+    edges = [
+        [
+            pygame.Vector2(1, 0),
+            lambda y: pygame.Vector2(-ASTEROID_MAX_RADIUS, y * SCREEN_HEIGHT),
+        ],
+        [
+            pygame.Vector2(-1, 0),
+            lambda y: pygame.Vector2(
+                SCREEN_WIDTH + ASTEROID_MAX_RADIUS, y * SCREEN_HEIGHT
+            ),
+        ],
+        [
+            pygame.Vector2(0, 1),
+            lambda x: pygame.Vector2(x * SCREEN_WIDTH, -ASTEROID_MAX_RADIUS),
+        ],
+        [
+            pygame.Vector2(0, -1),
+            lambda x: pygame.Vector2(
+                x * SCREEN_WIDTH, SCREEN_HEIGHT + ASTEROID_MAX_RADIUS
+            ),
+        ],
+    ]
+
+    def __init__(self):
+        pygame.sprite.Sprite.__init__(self, self.containers)
+        self.spawn_timer = 0.0
+
+    def spawn(self, radius, position, velocity):
+        asteroid = Asteroid(position.x, position.y, radius)
+        asteroid.velocity = velocity
+
+    def update(self, dt):
+        self.spawn_timer += dt
+        if self.spawn_timer > ASTEROID_SPAWN_RATE:
+            self.spawn_timer = 0
+
+            # spawn a new asteroid at a random edge
+            edge = random.choice(self.edges)
+            speed = random.randint(40, 100)
+            velocity = edge[0] * speed
+            velocity = velocity.rotate(random.randint(-30, 30))
+            position = edge[1](random.uniform(0, 1))
+            kind = random.randint(1, ASTEROID_KINDS)
+            self.spawn(ASTEROID_MIN_RADIUS * kind, position, velocity)