Example of HD simulations with embedded Jupiter-mass planet (planet_mass/star_mass−ratio = 10^-3). Color-coded is the H₂ number density in log scale. Left: midplane density. The planet has cleared out its orbit, producing a prominent gap. Owing to the perturbations, complex structures like spiral arms are also visible. Right: cut perpendicular to the disk midplane. The gap is clearly visible in the gas distribution. We note that the upper layers of the disk have nearly the same density as in the undisturbed case.