Left: Histories of volume-averaged mean ionization fraction ${\overline{x}}_{\mathrm{HII}}$ (top), mean 21 cm DBT ${\overline{T}}_{21\mathrm{cm}}$ (central), and rms of 21 cm DBT σ_21 cm (bottom) from simul_0.02 (solid cyan), simul_0.1 (solid red), simul_0.1_const (dashed red), simul_0.2 (solid yellow), simul_Fiducial (solid black), and simul_Fiducial_const (dashed black). Right: Redshift evolution of 21 cm power spectra Δ_21 cm² at k = 0.05 Mpc⁻¹ (top), 0.1 Mpc⁻¹ (central), and 0.5 Mpc⁻¹ (bottom) from the same simulations.