Game experience improvement

Thanks for playing my game and share your experience.

- At the beginning, the game only allow using mouse click and touch control, I heard some players feedback they are more used to use the arrow key to control this kind of game, so I add back the arrow control.

- Some players feedback that it will be nice if they can pause the game to take a break, or even control the music volume. So I added a pause game for volume control.

- Some players feedback that the game is too difficult, I think finding the balance of challenging and encouraging the player is very important, I have adjusted the game, to make it slow at the beginning and it will become more difficult when the player plays longer time. Wish this makes the game have more fun.