Add new sounds(soundtrack, engine, coin, explosion)
Change instructions(add soundtrack, instruction)
Change soundtrack file(KalimbaShort), Add function (get 1 live when player get 1000) to play.ts
add enemyBulletManager and enemyBullet
add enemybullet for playHard.ts, delete function(each 1000 get 1 live)
The logic of try again button? It always starts the easy one.