--- a/bot.py	Tue Mar 14 13:00:05 2017 +0100
+++ b/bot.py	Wed Mar 20 23:15:39 2019 +0000
@@ -2,23 +2,30 @@
 
 
 class Servo:
+    """A class for controlling continuous-rotation servos."""
+    
     def __init__(self, pin, trim=0):
-        self.pin = pin
-        self.trim = trim
-        self.speed = 0
-        self.pin.set_analog_period(20)
+        self.pin = pin  # The pin to which the servo is connected.
+        self.trim = trim  # What value makes the servo stop.
+        self.speed = 0  # Current speed.
+        self.pin.set_analog_period(20)  # Servo needs 20Hz signal.
 
     def set_speed(self, speed):
+        """Sets the rotation speed of the servo, range is -90 to +90."""
+        # Value of 25 gives us around 1000us, which is the minimum duty cycle
+        # for the servo. 125 is the maximum.
         self.pin.write_analog(int(25 + 100 * (90 + speed) / 180 + self.trim))
         self.speed = speed
 
 
 class Robot:
     def __init__(self):
+        # Initialize the servos. Adjust the trim as needed.
         self.left_servo = Servo(microbit.pin0, 2)
         self.right_servo = Servo(microbit.pin1, 1)
 
     def go(self, distance):
+        """Make the robot go straight for a given distance."""
         microbit.display.show(microbit.Image.ARROW_S)
         self.left_servo.set_speed(-90)
         self.right_servo.set_speed(90)
@@ -26,6 +33,7 @@
         self.stop()
 
     def turn(self, angle):
+        """Make the robot turn in place by given angle in degrees."""
         if angle > 0:
             microbit.display.show(microbit.Image.ARROW_E)
             self.left_servo.set_speed(-90)
@@ -39,24 +47,26 @@
         self.stop()
 
     def stop(self):
+        """Make the robot stop."""
         microbit.display.show(microbit.Image.DIAMOND)
         self.left_servo.set_speed(0)
         self.right_servo.set_speed(0)
 
     def get_distance(self):
+        """Use the distance sensor on pin2."""
         return microbit.pin2.read_analog()
 
 
-robot = Robot()
+robot = Robot()  # Create the robot object.
 while True:
-    robot.go(5)
-    if robot.get_distance() > 700:
-        robot.turn(20)
-        left_distance = robot.get_distance()
-        robot.turn(-40)
-        right_distance = robot.get_distance()
-        robot.turn(20)
-        if left_distance < right_distance:
+    robot.go(5) # Go forward 5 units.
+    if robot.get_distance() > 700:  # If the distance sensor returns something...
+        robot.turn(20) # Turn 20 degrees one way.
+        left_distance = robot.get_distance()  # Take a measurement.
+        robot.turn(-40) # Turn 20 degrees the other way (40 in total)
+        right_distance = robot.get_distance() # Take a measurement.
+        robot.turn(20) # Turn back straight.
+        if left_distance < right_distance: # Pick whatever side was further away.
             robot.turn(60)
         else:
             robot.turn(-60)