Go on a mobile device. Go here. https://llk.github.io/scratch-gui/ Put the URL in of this project. Go fullscreen Use joystick on bottom left to move. Use joystick on bottom right to shoot OR Just use your mouse on the joystick to simulate touchscreen to move.
The first step taken for mobile items. On PC, there is only one mouse. So if this went to mobile only one joystick can be used at a time. Hope this gets fixed for mobile preview!