Lego has a two-stud brick with a 45° slope that's used as a control panel on various vehicle kits, from automobiles to underwater craft to extraterrestrial shuttles. George Cave, a senior interaction technologist at KISKA in Salzburg Austria, collected 52 different Lego control panels and use them in a terrific mini-course in physical interface design.

Here's an excerpt:

Differentiating inputs

What could cause 400 WWII pilots to raise the landing gear on their B-17 bomber just before touchdown? Catastrophic pilot error, or something more fundamental?

It was the psychologist Alphonsis Chapanis who first suggested that the high rate of crash landings might be the fault of poor interface design. The adjacent landing gear and flap control knobs were identically shaped. The pilots never stood a chance.

B-17 belly landing, and the shape coding that helped to irradiate the problem. Source: Wikipedia

His temporary solution was to glue differently shaped strips of rubber to each switch, enabling blind operation by touch alone. This gave rise to the idea of shape coding and a system of differentiation still being followed in aircraft cockpits today.

We can compare the three interfaces [at the top] to see this in action. Ignore the overall layout, it’s the differences between individual switches that matter here. Imagine trying to feel for one of these buttons without looking. The left panel (“Slope 45 2 x 2 with 12 Buttons”) would require careful hand-eye co-ordination. The right panel (“Aircraft Multiple Flight Controls”) clearly distinguishes between the throttle (large, linear vertical movement), toggle switches (round vertical flick) and the push buttons (square push-in).

In the early 1980s, Susan Kare joined Apple Computer to design fonts and user interface graphics. A legend of pixel art, Kare created the look of the original Macintosh, from the Chicago typeface to the Trash Can to the Happy Mac icon. She's currently creative director at Pinterest. David Kindy profiles Kare in Smithsonian:

Pioneering designer Susan Kare was taught by her mother how to do counted-thread embroidery, which gave her the basic knowledge she needed to create the first icons for the Apple Macintosh 35 years ago.

“It just so happened that I had small black and white grids to work with,” she says. “The process reminded me of working needlepoint, knitting patterns or mosaics. I was lucky to have had a mother who enjoyed crafts..."

Designing the icons proved to be more of a challenge (than the typefaces). Reproducing artwork on those primitive CRT surfaces, which used a bit-mapped matrix system with points of light, or pixels, to display data, was a designer’s nightmare.

However, the friend who recommended Kare for the job—-Andy Hertzfeld, then lead software architect for Macintosh-—had an idea. Since the matrix was essentially a grid, he suggested Kare get the smallest graph paper she could find. She then blocked out a 32-by-32 square and began coloring in squares to create the graphics...

After leaving Apple in 1986, Kare became creative director for Apple cofounder Steve Jobs at the short-lived NeXT, Inc., an influential computer startup that was eventually acquired by Apple. She founded her own eponymous design firm in 1989, which created graphic designs for hundreds of clients, including Autodesk, Facebook, Fossil, General Magic, IBM, Microsoft and PayPal.