The rules differ from print comics. The grammar that scrolling created.
Print comics show two pages at once, so layout guides the eye and the page turn itself becomes a tool for reveals. Vertical scroll flows only downward, and what comes next is not visible. That one-way movement is the starting point for vertical staging.
Widening the gap between panels lengthens the time the reader spends scrolling, and the story time feels longer to match. Deliberately stretching empty space to build tension or leave an aftertaste is the signature technique of the format. Packing panels tightly does the opposite and moves quickly.
The vertical span visible at once is effectively the unit of staging. An image meant to land hard needs enough gap that it does not share a screen with what precedes it. Screen sizes differ between readers, so exact control is impossible and generous spacing is the usual safeguard.
Side-by-side bubbles create ambiguity about reading order in a vertical format. Stacking dialogue vertically to make the order unambiguous is therefore common. Too much dialogue in one screen slows reading sharply, so long conversations are spread across several panels.
Most readers use phones, so dark scenes can be nearly invisible in bright surroundings. Keeping contrast generous and checking on an actual small screen is part of the process. Some readers also use dark mode, so staging that assumes white margins can read differently from the intent.
Each button runs this keyword on that search engine