When looking at a single screen, the button shape and centering is consistent. Further, a primary button is called out using size, color, and placement – in line with interface guidelines.
Stop up top on the Timer, stop down at the bottom on the Alarm. The Timer and Alarm designs look so similar that visual/muscle memory can lead you to tap the wrong button. Confusing!
Ah, this is what you really want. A design steeped in context. It’s an alarm clock, and you often want to snooze one of those – especially early in the morning when you’re randomly smacking at things, hoping to hit the right thing. So make Snooze huge – no more hunting for that small button in a field of black. And make stop larger too. You could use this with your eyes closed as long as you know the shape of the phone, and which side is up/down. (Note: this is a conceptual design by Alex Cornell)