"Alphabet Zoo" A typing game in Python - 1.0

My Game will start after user click the Play Button. Random letters fall down from the top of the screen after a time interval and the letter will vanish while you strike the corresponding key on the keyboard. The falling and generating speeds of letters will accelerate as the game progresses. Game is over when more than 10 letters have reached the bottom. There is a scoring system set for this game. You'll get 50 points if you strike the correct letter and miss 50 points if you strike the wrong one. Besides, different sound effects are avail