Designing a Shopping App: What Changes When the Screen Is a Thumb
A phone is not a small desktop, and a catalogue laid out like one fails.
A phone is not a small desktop
The difference is not width, it is attention and reach. One thumb, held one-handed, usually while doing something else. Anything above the middle third of the screen is hard to reach and anything below it is where the important controls belong — which is the opposite of where a desktop puts them.
Start from what the catalogue is
A fashion catalogue sells on the photograph, so the layout leads with the image. A consumables catalogue sells on re-ordering, so search and order history matter more than the hero. A brand-led catalogue sells on the label, so the brand list is a first-class screen. The same layout cannot serve all three.
The five decisions that shape everything else
What the home screen leads with. How deep the category tree goes. Whether the product page is gallery-first or variant-first. What occupies the five tab-bar slots. And where the search field lives.
What to resist
Putting everything on the home screen because it all matters. It does, and the result is a screen where nothing does. Choose the one thing the customer came for and let the rest be one tap away.
What we would actually tell you
An app earns its keep on repeat purchases. If your customers buy once and have no reason to return, no amount of design changes that, and we would say so on a call rather than take the money. If they do come back — for a new season, a refill, a replacement — then the question is only whether you reach them for free or pay for them twice.