Angle of the phase-space spiral at the iso-energy contour E_z = Φ(200 pc) in the (z, w)-plane, as inferred in Widmark et al. (2022b). The colour bar is cyclical. If the angle is close to 0 (or 2π, equivalently), then the spiral perturbation corresponds to an over-density at the phase-space coordinates (Z, W) = (200 pc, 0 km s⁻¹); conversely, if the angle is close to π, then the spiral corresponds to an under-density at (Z, W) = (200 pc, 0 km s⁻¹). Area cells that are crossed over in white are marked as less trustworthy; we refer to Widmark et al. (2022b) for details.