##-------- kychann, KangsikWoo, YunJ --------##

1. Adding Left and Right Movement:
 - In the original code, the ball could only move up (UP) and down (DOWN).
 - After the modification, left (LEFT) and right (RIGHT) movement has been added.
2. Code Structure Improvement:
 - The original code structure was preserved as much as possible while making minimal and concise changes.
 - Unnecessary comments were removed to improve code readability.