This main function will be the first the first function called at runtime and will be responsible from calling all the other functions defined in the code.
In this case it is setting the initial difficulty of the game as well as the maximum difficulty to be cleared to complete the game. The while loop is the main game loop of the game in which is checks if the game is going to continue running using the while condition to check is the current difficulty is less than or equal to the maximum difficulty.
Within the game loop it calls the play game function by passing in the current difficulty. After the game function finishes it will do some clean up operations that I don’t really understand and then increment the difficulty for the next iteration.
The game loop will terminate when the difficulty exceeds the maximum difficulty, triggering the “win state” and the process will stop running.