import graph3;

size(8cm,0);
currentprojection=orthographic(1,1,1);

bbox3 b=limits((-2,-2,0), (0,2,2));
aspect(b,1,1,1);

xaxis("$x$", b, RightTicks());
yaxis("$y$", b, RightTicks());
zaxis("$z$", b, RightTicks());