CALL SPRITE is built into SmileBasic. You can actually use CALL to call most any function passed as a string. Anyway, you set up what function to call or line to jump to with SPFUNC. Then CALL SPRITE will look at every sprite. If it has a SPFUNC value it will set CALLIDX to the sprite's handle and call the function. If you set it up right, the sprites move around on their own.