'chapter 12
'qix line drawing
'requires CyBasic-2
'see below for CyBasic-1

dim n as int
print "Number of lines"
input n

dim n1 as int
dim n2 as int
n1=n-1
n2=n1-1

dim x0[n] as int
dim y0[n] as int
dim x1[n] as int
dim y1[n] as int
dim dx0 as int
dim dy0 as int
dim dx1 as int
dim dy1 as int
dim seed as int

sub newdirection(j as int)
  if (x0[j] < -80 or x0[j] > 80) then
    dx0 = -dx0
  end if
  if (x1[j] < -80 or x1[j] > 80) then
    dx1 = -dx1
  end if
  if (y0[j] < -43 or y0[j] > 43) then
    dy0 = -dy0
  end if
  if (y1[j] < -80 or y1[j] > 80) then
    dy1 = -dy1
  end if
end sub

' for cybasic1 do the following
' dx0=-3
' dx1=-1
' dy0=1
' dy1=2
'and remove the while loops...

' select random motion offsets
while dx0=0
  dx0 = 4-rnd(9)
wend
while dx1=0
  dx1 = 4-rnd(9)
wend
while dy0=0
  dy0 = 4-rnd(9)
wend
while dy1=0
  dy1 = 4-rnd(9)
wend

'select initial random line
x0[0] = rnd(80)
x1[0] = rnd(80)
y0[0] = rnd(43)
y1[0] = rnd(43)
line x0[0], y0[0], x1[0], y1[0]

cls

'fill up queue with trailing lines and print them
for i=1 to n-1
  x0[i] = x0[i-1] + dx0
  x1[i] = x0[i-1] + dx1
  y0[i] = y0[i-1] + dy0
  y1[i] = y1[i-1] + dy1
  line x0[i], y0[i], x1[i], y1[i]
  newdirection(i)
next

for i=0 to 1 step 0
  ink 0
  line x0[0], y0[0], x1[0], y1[0]
  ink 3
  for j=1 to n-1 
    x0[j-1] = x0[j]
    x1[j-1] = x1[j]
    y0[j-1] = y0[j]
    y1[j-1] = y1[j]
  next
  x0[n1] = x0[n2] + dx0
  y0[n1] = y0[n2] + dy0
  x1[n1] = x1[n2] + dx1
  y1[n1] = y1[n2] + dy1
  line x0[n1], y0[n1], x1[n1], y1[n1]
  newdirection(n1)
next