Virtual Joystick
When sdlBasic don't detect a real joystick attached to your pc a virtual joystick is emulated by using the keyboard.
Keys
Virtual joystick ergonomy is based upon the GP2X handheld device.
Here a picture of the device.

direction are emulated by arrow keys or, in alternative, the keys on numeric pad.
left and right shift keys emulates the two front buttons
Keys A S D F emulate buttons A B X Y
Page Up and Down are used to emulate volume buttons
Select and Start are emulated using Keys ? ?