import three;

size(7cm);
currentprojection=orthographic(5,4,3);

triple pA=(2,2,0), pB=(-2,2,0), 
       pC=(-2,-2,0), pD=(2,-2,0),
       pS=(0,0,5);

draw(pA--pB--pC--pD--cycle);
draw(pA--pS--pB^^pC--pS--pD);