'===========================================================================
' Subject: VGA BOUNCING LINES DEMO           Date: 02-06-97 (14:05)       
' Author:  Dave Navarro, Jr.                 Code: PB                     
' Origin:  dave@powerbasic.com             Packet: GRAPHICS.ABC
'===========================================================================
' VGA bouncing lines demo for PowerBASIC
' by Dave Navarro, Jr.

RANDOMIZE TIMER

DEFINT A-Z

SCREEN 12

z = 40

DIM x1(1:z), x2(1:z), y1(1:z), y2(1:z)
DIM a1(1:z), a2(1:z), b1(1:z), b2(1:z)

x1 = (RND * 640) : x2 = (RND * 640)
y1 = (RND * 480) : y2 = (RND * 480)
a1 = (RND * 640) : a2 = (RND * 640)
b1 = (RND * 480) : b2 = (RND * 480)

c1  = 9 : c2  = 14

xd1 = 9 : xd2 = 7
yd1 = 6 : yd2 = 10
ad1 = -11 : ad2 = 7
bd1 = 4 : bd2 = -13

DO

  ARRAY DELETE x1(1) : ARRAY DELETE x2(1)
  ARRAY DELETE y1(1) : ARRAY DELETE y2(1)
  ARRAY DELETE a1(1) : ARRAY DELETE a2(1)
  ARRAY DELETE b1(1) : ARRAY DELETE b2(1)

  LINE (x1, y1) - (x2, y2), c1
  LINE (x1(1), y1(1)) - (x2(1), y2(1)), 0
  LINE (a1, b1) - (a2, b2), c2
  LINE (a1(1), b1(1)) - (a2(1), b2(1)), 0

  x1(z) = x1 : x2(z) = x2
  y1(z) = y1 : y2(z) = y2
  a1(z) = a1 : a2(z) = a2
  b1(z) = b1 : b2(z) = b2

  INCR x1, xd1 : INCR x2, xd2
  INCR y1, yd1 : INCR y2, yd2

  INCR a1, ad1 : INCR a2, ad2
  INCR b1, bd1 : INCR b2, bd2

  IF (x1 < 1) OR (x1 > 638) THEN
    xd1 = 0 - xd1
  END IF

  IF (x2 < 1) OR (x2 > 638) THEN
    xd2 = 0 - xd2
  END IF

  IF (a1 < 1) OR (a1 > 638) THEN
    ad1 = 0 - ad1
  END IF

  IF (a2 < 1) OR (a2 > 638) THEN
    ad2 = 0 - ad2
  END IF

  IF (y1 < 1) OR (y1 > 478) THEN
    yd1 = 0 - yd1
  END IF

  IF (y2 < 1) OR (y2 > 478) THEN
    yd2 = 0 - yd2
  END IF

  IF (b1 < 1) OR (b1 > 478) THEN
    bd1 = 0 - bd1
  END IF

  IF (b2 < 1) OR (b2 > 478) THEN
    bd2 = 0 - bd2
  END IF

  INCR x

  IF x = 1000 THEN
    INCR c1
    INCR c2
    IF c1 = 16 THEN c1 = 9
    IF c2 = 16 THEN c2 = 9
    x = 0
  END IF

  DELAY .08

LOOP UNTIL LEN(INKEY$)

SCREEN 0