Talk to a station keeper, step through a passage, crack a cover, haul in a wreck, prise a Pearl shell, throw the net at something in range — every one of these draws its own tap ring on a touch screen now, and tapping the ring fires the exact action, through the same handler the T or C key fires on a keyboard. It used to only mean "something here answers to a key you don't have" and send you looking for the labelled button in the corner. That button still exists, right where it always sat, as a second way to do the same thing — but it was never meant to be the only way, and now it isn't.
One thing worth knowing if you've caught something rare and stared at two glowing shapes wondering which one's the button: a rarity-coloured halo on a creature or a warm glow on a crystal is a STATE, saying "this is worth having" — it isn't tappable on its own. The filled, hard-edged ring is the CONTROL. They can share the same object at once, and only the ring answers a tap.
Pearl shells also draw a tap ring now for the first time — they used to show only that same soft glow and nothing else, so nothing on any device, keyboard included, actually said the arm could prise one open. And any tap the game recognises but can't act on — a cover still locked, an arm too weak for the haul — gets a plain explanation the first time it happens, then the same short refusal every time after. Full breakdown in the guide: Playing on Mobile.