The Indiepinion

George Fan, Lead Designer of Plants vs. Zombies in an interview:

… regarding the plant cards on the top border of the screen with respect to all WOW players who are used to have their skill buttons at the bottom …

To the extent that it’s actually quite surprising that you didn’t put them at the bottom of the screen just so it would drive it home that that’s the way that you interact with them.

Yeah… [pauses] I don’t know why. That’s a good point. I don’t know why they’re not at the bottom of the screen [laughs]. I think we just put them up top and no one complained. I never thought to rework that. We actually had a little bit of a problem with getting the sun to fall from the top behind or in front of the… Okay, well if there’s a sequel we’ll change it. Thanks for that suggestion!

It’s simple, really … Windows puts the taskbar at the bottom ever since ’95.

So putting essential buttons on the bottom of the screen may just be following a Microsoft standard the wrong way (the Windows taskbar contains non-essential elements) … or id Software’s for that matter – remember Doom?

I say topmost buttons work best if they’re essential and used often (such as a program’s menu for example) … it feels more natural if that’s the main way to interact or if they are elements you need to focus on. Most likely because humans (and possibly Zombies, too) “read” from top to bottom … so i like that they’ve put them at the top in Plants vs Zombies. World of Warcraft isn’t necessarily wrong though – consider that WoW is a 3D world game where most of the interesting game elements reside in the bottom half of the screen (on the floor). So it makes more sense for them to have the action buttons at the bottom.

Needless to say my Windows taskbar is at the top ever since ’95 … but that’s just me being non-conformist.

I also keep a lot of essential elements up there … maybe too many for some. That’s just me not wanting to use the Start menu.