SCREEN 13

FOR i = 0 TO 320 STEP 10
  LINE (0, i)-(319, i), 5
  LINE (i, 0)-(i, 199), 5
NEXT i

LINE (0, 100)-(319, 100), 10

PRINT "press a key..."
a$ = INPUT$(1)

y = 100
ys = -1
FOR t = 0 TO 300
  PSET (t, y), 14
  ys = ys + .01
  y = y + ys
  SOUND 300 - y, .1
NEXT t