Jobs obsessed with equal intensity about the look of what would appear on the screen.
One day Bill Atkinson burst into Texaco Towers all excited.
He had just come up with a brilliant algorithm that could draw circles and ovals onscreen quickly.
The math for making circles usually required calculating square roots,
which the 68000 microprocessor didn't support.
But Atkinson did a workaround based on the fact that
the sum of a sequence of odd numbers produces a sequence of perfect squares (for example, 1+3=4, 1+3+5=9, etc.).
Hertzfeld recalled that when Atkinson fired up his demo, everyone was impressed except Jobs.
"Well, circles and ovals are good," he said,
"but how about drawing rectangles with rounded corners?"
"I don't think we really need it," said Atkinson, who explained that it would be almost impossible to do.
"I wanted to keep the graphics routines lean and limit them to the primitives that truly needed to be done," he recalled.
"Rectangles with rounded corners are everywhere!" Jobs said, jumping up and getting more intense.
"Just look around this room!"
He pointed out the whiteboard and the tabletop and other objects that were rectangular with rounded corners.
"And look outside, there's even more, practically everywhere you look!"
He dragged Atkinson out for a walk, pointing out car windows and billboards and street signs.
"Within three blocks, we found seventeen examples," said Jobs.
"I started pointing them out everywhere until he was completely convinced."
"When he finally got to a No Parking sign, I said,'Okay, you're right, I give up.
We need to have a rounded-corner rectangle as a primitive!'"
Hertzfeld recalled, "Bill returned to Texaco Towers the following afternoon, with a big smile on his face.
His demo was now drawing rectangles with beautifully rounded corners blisteringly fast."
The dialogue boxes and windows on the Lisa and the Mac,
and almost every other subsequent computer, ended up being rendered with rounded corners.