Add comments to tail example

examples/basic/tail.py

@@ -1,35 +1,48 @@
 from math import sin, cos
+
+# Constants that control the wobble effect
 SEGMENT_SIZE = 50
 ANGLE = 2.5
 PHASE_STEP = 0.3
 WOBBLE_AMOUNT = 0.5
 SPEED = 4.0
 
-tail = [
-    Actor('tail_piece') for _ in range(10)
-] + [Actor('tail_hook')]
-
-
+# Dimensions of the screen
 WIDTH = 800
 HEIGHT = 800
 
+# The sprites we'll use.
+# 10 tail pieces
+tail = [Actor('tail_piece') for _ in range(10)]
+# Plus a hook piece at the end
+tail += [Actor('tail_hook')]
+
+# Keep track of time
 t = 0
 
 
 def draw():
     screen.clear()
+    # First draw the even tail pieces
     for a in tail[::2]:
         a.draw()
+    # Now draw the odd tail pieces
     for a in tail[1::2]:
         a.draw()
 
+
 def update(dt):
     global t
     t += dt
+    # Start at the bottom right
     x = WIDTH - SEGMENT_SIZE // 2
     y = HEIGHT - SEGMENT_SIZE // 2
     for seg, a in enumerate(tail):
         a.pos = x, y
+
+        # Calculate an angle to the next piece which wobbles sinusoidally
         angle = ANGLE + WOBBLE_AMOUNT * sin(seg * PHASE_STEP + t * SPEED)
+
+        # Get the position of the next piece using trigonometry
         x += SEGMENT_SIZE * cos(angle)
         y -= SEGMENT_SIZE * sin(angle)