techradar.com has an interesting article on UI changes that were considered for Windows 7, but didn’t make it into the final product.
The next prototype, in February 2007, was called the Bat Signal; when you moved your mouse over an icon in the taskbar, the full window would pop up on screen, highlighted by beams of light (a little like the Batman signal projected over Gotham City).
Bat Signal made it easy to find the right window but it caused other problems: «sometimes people toss the mouse down to the bottom of the screen when they’re typing because they don’t care where the mouse is and the Bat Signal pops up and that’s really intrusive in their flow.»
The article also spends some time going into why some of the features were dropped and how Microsoft uses data to make user interface decisions.
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