[refactor] Move objets to separate files.

- ball
- bricks
- paddle
Update documentation and readme.
[fix] Game over: update player score.

ball.py

@@ -0,0 +1,54 @@
+from random import randint
+
+from screen import Screen, WHITE
+from paddle import Paddle
+
+BALL_SPEED = 3
+
+
+class Ball:
+    def __init__(self, screen: Screen, paddle: Paddle, radius: int, color: int = WHITE, brick_padding: int = 0, speed: int = BALL_SPEED): 
+        self.screen_width = screen.width
+        self.screen_height = screen.height
+        self.radius = radius
+        self.color = color
+        self.speed = speed
+        self.x_speed = self.speed if randint(0, 1) == 0 else -self.speed
+        self.y_speed = -self.speed
+        self.brick_padding = brick_padding
+        self.reset_pos(paddle)
+
+    def reset_pos(self, paddle: Paddle):
+        """Reset ball position to the center of the paddle."""
+        self.x = self.screen_width // 2
+        self.y = self.screen_height // 2 - self.radius - 2
+        self.x_speed = self.speed if randint(0, 1) == 0 else -self.speed
+        self.y_speed = -self.speed
+
+    def update_pos(self):
+        """Update ball position."""
+        self.x += self.x_speed  
+        self.y += self.y_speed  
+
+        # Bounce off left or right screen edge
+        if self.x < 0:
+            self.x = 0
+            self.x_speed = -self.x_speed
+        elif self.x > self.screen_width - self.radius:
+            self.x = self.screen_width - self.radius
+            self.x_speed = -self.x_speed
+
+        # Bounce off top screen edge
+        if self.y < self.brick_padding + self.radius:
+            self.y = self.brick_padding + self.radius
+            self.y_speed = -self.y_speed
+
+        # Drop through bottom screen edge & return True to indicate we lose a life
+        if self.y > self.screen_height:
+            self.y = self.screen_height
+            self.y_speed = -self.y_speed
+            return True
+
+    def draw(self, screen: Screen):
+        """Draw ball."""
+        screen.fbuf.ellipse(self.x, self.y, self.radius, self.radius, self.color, True)