Simple Pygame game

please explain code in detail

Develop a game that includes the following attributes: The player controls a red square with the arrow keys. A blue circle will appear at a random position whose diameter is initially equal to the length of the square. The circles diameter is to decrease by 1/4 every second. The player has to capture the circle before it disappears. If the player captures the circle the game continues. Once the circle disappears the game is over