Evolution of the eccentricity and resonant angle for the 2p20LH IB model when the planets are engaged in 3:2, 4:3, and 5:4 resonances, respectively (panels a–c). Panel d: evolution of orbital period ratio. The colour-coding corresponds to the right panel and indicates the time evolution of the noted resonances in panels a–c. Explicitly, blue in panel a–c indicates the time before the system forms resonance, which is noted at the top of each panel and also in panel d, and red represents the time after the system is in resonance. The exact time can be extracted from comparing the colours in panel d with those in panels a–c.