Back when I started out on Mobile Device Manager Plus at ManageEngine, I reviewed our design proposals before they reached development. We’d go through a couple of iterations on Figma, then leadership sign-off. A careful process.
But some flaws slip through it anyway, without ever looking wrong.
What do you find odd about the prototype below?
If you’ve already spotted it, you’ve learned the lesson. If not, no surprise. It looks perfectly fine sitting still. Grab the scrollbar and drag it down.
Have you found the lesson yet? The page number sits right under your thumb. The designer wants you reading it while you scroll, but your thumb is covering it the whole time. Not a usable design.
With enough practice, PMs can spot a lot of these just by looking at the frames on screen. But some flaws only show themselves under a real thumb.
My time at MDM and Arattai taught me to review a design on the thing people will actually hold. If it ships on a phone, review it on a phone. If it ships on a tablet, review it on a tablet. Same for a watch, a TV, a shared kiosk in a shop. The medium, the dimensions, the peripherals your real users use: all of it is how you get close to them. Anything you judge from a comfy desk on a 27-inch monitor is a guess about somebody else’s thumb.
Most design tools already have a mobile preview, so you can experience the design on a real screen with almost no effort. And with Claude Code and the like, it’s easier than ever to build the interaction as a quick HTML/CSS file and try it on your phone before you move forward.
Iteration is the only way to usable design. Don't try to shortcut it.