What can go wrong with a keypad design? Not much, we could think. Actually there are several things to make the interface easier to use (or usable at all!). Let’s see some examples.
Google Voice interface. Image from funkyspacemonkey.com
It’s difficult to imagine a keypad interface clearer than the one of Google Voice for iPhone. Everything is in the right place, there are no possibilities for confusion.
The Android interface. Picture by xda-developers.com
The Android keypad is not bad, but I’m a little bit skeptical about the lack of separation among the number columns and about the fact that buttons don’t look like buttons. Still, I think it might work pretty well most of the time.
Windows Mobile keypad interface. Picture by extremeppc.com
The Windows Mobile keypad interface could be a little bit confusing, I don’t like the fact that numbers are located on the right side of the buttons (instead of being in the center). Some people, specially the ones with big fingers, might accidentally press on the wrong button if they try to tap on the number and not in the center of the button. This configuration could also be a little bit disturbing for the users’ eye, humans tend naturally to look for symmetric signs and this buttons lack of that harmony.
Door keypad in Starbucks. Picture by Alexis Brion.
The last example is coming from the physical, real, world, not from a software interface. This is the keypad to unlock the toilet door at the Starbucks located in the Düsseldorf central station. I was sitting close to it and I couldn’t help watching the clients fail several times when trying to enter the code. Numbers are not located on the buttons, they are below them. Users were confusing labels: which is the number 5 button?
