Beating period of the two main frequencies (P_beat) against the normalised percentile amplitude ratio (A_var). Light curves manually classified as mono-periodic are shown in purple, multi-periodic in olive, hybrids in red, and other cases in cyan. The dashed lines indicate the approximate dividing lines of the groups of pulsating stars. Uncertainties on the beating period are within the symbol sizes (A_var has no formal uncertainty due to its definition).