Spartan calculates the structure and spectrum of optically thin advection-dominated accretion flows (ADAFs) by solving the disk equations numerically under a geometrically thin-disk assumption, using height-integrated equation sets. It reads physical and numerical parameters, including black hole mass, accretion rate, viscosity, pressure ratio, adiabatic index, spin, electron heating fraction, frequency and radial grids, radial step-size controls, specific angular momentum limits, and inclination angle. Spartan returns intrinsic and observed spectra, global disk solutions, and spectra at each radius, and supplies tools to visualize the disk structure and spectral output.