set terminal postscript eps color solid enhanced size 10cm,8cm font "Helvetica,18pt"
set output "contour.eps"

h(x,y)=x**2+y**2

set hidden3d
set contour both
# set xyplane at -50

set xrange [-12:12]
set yrange [-12:12]

set samples 20
set isosamples 21

set xlabel "x" font "Times-Italic,24" offset -0.5,-0.5
set ylabel "p" font "Times-Italic,24"
set zlabel "H" font "Times-Italic,24" offset 3,6

set cntrparam levels discrete 20, 50, 100, 150

set linetype 1 lc rgb "red"
set linetype 2 lc rgb "green"
set linetype 3 lc rgb "black"
set linetype 4 lc rgb "black"
set linetype 5 lc rgb "black"
set linetype 6 lc rgb "black"

set xtics offset -0.3,-0.3
set ytics offset 0.3, -0.3

splot  h(x,y) w l nosurface notitle