The 21 cm brightness temperature with all fluctuations included. Dotted – simulation S1, solid – simulation S2, dashed – simulation S3. Redshifts from top to bottom are: 19.25 (⟨ x_α ⟩  = 0.9), 20.25 (⟨ x_α ⟩  = 0.4), 22.5 (⟨ x_α ⟩  = 0.06). The black dash-dotted line shows the correction for  ⟨ x_α ⟩  = 0.4 when doing the full Lyα flux inhomogeneous integration.