Develop a simple class based Python ball game

I have a very simple ball game (which uses classes). The player ball (black) can move around the screen using the arrow keys. If it collides with the red ball, the score variable goes down. If it collides with the green ball, the score variable increases. The file is attached. I now need to add the following things to this game, and would like it done in individual files, showing each developmental step. I would like the added code to be carefully and logically commented to explain what is being done. File 0 - attached: A ball game. Player ball, enemy ball (red), score ball (green). File 1 - Add a Menu Screen. P - Play Q - Quit S - Save High Scores V - View High Scores. This Menu screen should be drawn on the screen at game-start. The user can select an option. File 2 - Add a timer function to the game. 20 seconds for game play. If the score reaches 100 within 20 seconds, add a feature to say "Game won". If 20 seconds is over and 100 has not been achieved, "You Lose". File 3 - Add the high scores save and view feature to the game. The first three high scores are stored in a file (Name: Score). If the user 'wins', they can add their high score to the file (Press S on the Menu). Pressing 'V' would enable the high scores from the file to be viewed (displayed on screen) File 4 - Add an angel sprite to the game. The angel sprite drops like a bullet from the top of the screen at three random intervals and from three random positions each time. If the player ball collides with the angel sprite, the score jumps to 100 each time. File 5 - An a devil sprite to the game. The devil races across (horizontally) like a bullet from left to right on the screen at three random intervals, and from different random starting positions. If the player ball collides with the devil sprite, the score is decremented -100 each time! File 6 - Add a Level Feature to the game. IF the player achieves a 200 point score, the player is taken to the NEXT level. On the next level there is a background of clouds. There is a very fast moving green ball (which increments score) and two medium-large sized red balls that decrement score (making the game thus harder). The same rules apply. In 20 sceonds, if '300' is not achieved, the game is over. Note: the score continues from Level 1 (in which it was 200). Again, these are given the option to be added to the high scores text file. As mentioned above, I want each of these done in separate python files to show the development and coding/with comments of each stage.