//Harvard Bridge

set forecolor 100
set backcolor 0

command solidrect x1 y1 x2 y2
{
   pen forecolor
   repeat y y1 y2
   {
      line x1 y x2 y
   }
}

command rect x1 y1 x2 y2
{
   pen forecolor
   repeat y 0 ((y2-y1)/3)
   {
      line x1 (y1+y*3) x2 (y1+y*3)
   }
}

command recthatch x1 y1 x2 y2
{
   pen forecolor
   repeat y 0 ((y2-y1)/5)
   {
      line (x1+y*5*(x2-x1)/(y2-y1)) y1 x1 (y1+y*5)
      line (x2-y*5*(x2-x1)/(y2-y1)) y1 x2 (y1+y*5)
   }
   repeat y 0 ((y2-y1)/5)
   {
      line (x2-y*5*(x2-x1)/(y2-y1)) y2 x1 (y1+y*5)
      line (x1+y*5*(x2-x1)/(y2-y1)) y2 x2 (y1+y*5)
   }
}

command streamer xi yi xv yv
{
   set x xi
   set y yi
   repeat i 1 10
   {
      set x (x+xv)
      set y (y+yv)
      set [x y] forecolor
      set [x (y-1)] forecolor
      set [(x+1) y] forecolor
      set [x (y+1)] forecolor
      set [(x-1) y] forecolor
      set yv (yv-2)
   }
}

command connect_sqr x1 y1 x2 y2
{
   set cx ((x1+x2)/2)
   set cy ((y1+y2)/2)
   set of forecolor
   set forecolor 33
   recthatch (cx+(y1-cy)) (cy+(x2-cx)) (cx+(y2-cy)) (cy+(x1-cx))
   set forecolor of
   pen forecolor
   line (cx+(y1-cy)) (cy+(x2-cx)) x2 y2
   line (cx+(y1-cy)) (cy+(x2-cx)) x1 y1
   line (cx+(y2-cy)) (cy+(x1-cx)) x2 y2
   line (cx+(y2-cy)) (cy+(x1-cx)) x1 y1
}

forever
{
   set a <mouse 1>
   set b <mouse 2>
   smaller? ((50-a)*(50-a)+(50-b)*(50-b)) 100
   {
      set a 50
      set b 50
   }
   paper 0
   set forecolor 100
   solidrect a b (a*2) (b*2)
   set forecolor 66
   rect (100-((100-b)/2)) (100-((100-a)/2)) b a
   set forecolor 25
   streamer 20 50 6 10
   set forecolor 50
   streamer 24 54 10 6
   set forecolor 50
   streamer 20 54 10 10
   set forecolor 0
   streamer 24 50 6 6
   set forecolor 100
   connect_sqr 10 10 a b
}