How do I order the refills (which column fills first)?

setDropOrder('all' | 'ltr' | 'rtl' | [perReelDelaysMs]) chooses which reel refills first -- simultaneous, a left-to-right wave, right-to-left, or explicit per-reel delays. Which cell inside a reel lands first is a separate knob: .tumble({ dropIn: { cellOrder: 'endFirst' | 'startFirst' } }).