Left panel: distribution of the ionisation levels of the N slices that can be carved out of the rsage const simulation along one direction. Each colour corresponds to one of 12 snapshots taken on the range 6.02 ≤ z ≤ 14.63, corresponding to different ionisation levels, represented as the solid vertical lines. Right panel: evolution of the standard deviations of each distribution with global reionisation history (blue solid line), compared to the standard deviation of the distribution of ionised pixels throughout the whole box (dashed line, divided by 10).