mode_setup;
beginchar(50,25/3pt#,20/3pt#,0);
s=5pt; % side of the square
z1=(0,0); z2=(s,0); z3=(0,s); z4=(s,s);
for k=1 upto 4: z[k+4]=z[k]+(2/3s,1/3s); endfor
pickup pencircle scaled .4pt;
draw z5--z6--z8--z7--cycle;
cullit; pickup pencircle scaled .8pt;
undraw z2--z4--z3;
cullit; pickup pencircle scaled .4pt;
draw z1--z2--z4--z3--cycle;
for k=1 upto 4: draw z[k]--z[k+4]; endfor
labels(1,2,3,4,5,6,7,8); endchar;

beginchar(51,25/3pt#,20/3pt#,0);
z1=(0,0); z2=(s,0); z3=(0,s); z4=(s,s);
for k=1 upto 4: z[k+4]=z[k]+(2/3s,1/3s); endfor
pickup pencircle scaled .4pt;
draw z3--z4; draw z5--z6;
cullit; pickup pencircle scaled .8pt;
undraw z7--1/3[z7,z5]; undraw z2--1/3[z2,z4]; showit;stop "see?";
undraw z7--1/2[z7,z5]; undraw z2--1/2[z2,z4]; showit;stop "(better)";
cullit; pickup pencircle scaled .4pt;
draw z3--z1--z2--z4; draw z5--z7--z8--z6;
for k=1 upto 4: draw z[k]--z[k+4]; endfor
labels(1,2,3,4,5,6,7,8); endchar;