Problem with Joystick

Im new and im using the free unity version. when im trying to run the game it says: all compoiler problems have to be fixed before you can enter playmode i dont know how to fix the errors and i didnt found answer. how to fix it? the errors are: Assets/Standard Assets (Mobile)/Scripts/SidescrollControl.js(15,20): BCE0018: The name 'Joystick' does not denote a valid type ('not found'). And Assets/Standard Assets (Mobile)/Scripts/SidescrollControl.js(14,20): BCE0018: The name 'Joystick' does not denote a valid type ('not found').