Here is the code again...
MoveBall:
REM Figure out the slope and multiply that into the BALLX and BALLY
SLOPEX = OLDX - BALLX
SLOPEY = OLDY - BALLY
REM Detect Paddle hitting the ball
IF SPRITE HIT(2,1) = 0
OLDX = SPRITE X(2)
XDIRECTION = XDIRECTION * -1
ENDIF
REM Detect the ball leaving the screen over the x axis
IF BALLX > (SCREEN WIDTH() - BALLXBOTTOM) OR BALLX < 0
OLDX = SPRITE X(2)
XDIRECTION = XDIRECTION * -1
ENDIF
REM Detect the ball leaving the screen over the y axis
IF BALLY > (SCREEN HEIGHT() - BALLYBOTTOM) OR BALLY < 0
OLDY = SPRITE Y(2)
YDIRECTION = YDIRECTION * -1
ENDIF
REM Increment the ball with its move rate and make sure the ball is heading in the right direction
BALLX = (BALLX + BALLMOVERATE) * XDIRECTION
BALLY = (BALLY + BALLMOVERATE) * YDIRECTION
BALLX = BALLX + (BALLX * SLOPE)
BALLY = BALLY + (BALLX * SLOPE)
SPRITE 2,BALLX,BALLY,2
RETURN