Animations in Windows Phone 7
An interesting overview of teases and transitions in Microsoft’s new mobile OS:
[Natural User Interfaces] frequently need to let people know what elements are interactive. (Ideally everything is interactive in a touch-based UI but that’s a different point.) NUIs should encourage exploration and give people “permission” to touch things. Teasing people is one way of encouraging interactivity and exploration.
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Transitions also help communicate interactions. When users move between screens, interaction components fly in or swivel highlighting the fact they are active and can be touched. Once someone taps on these components, they pivot or recede as if they were pushed backward into space. This animation…reinforces the fact they are active.
— Windows Phone: User Interface Teases & Transitions, lukew.com, February 17, 2010