When you’re diagnosing a usability snag, or coming up with a new design idea, it’s helpful to know what level you’re working at. Over the years, designers and researchers have defined various levels, reflecting their view of design and what they emphasize. I find the following scheme most helpful: Physical. If you want to think of levels as low and high, this one is at the bottom. It’s the level of design in which you’re concerned about the physical (and physiological) qualities of ...
