LC = "'white'" 
set term gif animate delay 10 size 480,360 backg "#003366"\
  font "/usr/share/fonts/TrueType-dejavu/DejaVuSansCondensed.ttf,10"
set out "diffusion.gif"
set samples 200
set tics tc @LC
set border lc @LC
set key tc @LC

D = 10
do for [i = 2:50] {
  t = i * 0.005
  plot [-10:10] [0:1] exp(-x**2/(4*D*t))/(2*sqrt(pi*D*t)) lw 2 lc @LC
}