点击主按键后，一个小的卡式窗口中就会显示当前正在运行的程序，这时就可以随意地向左或向右选择卡片，也就是选择程序。
Hit the physical home button, and each app currently running is displayed in a small Card window. Swipe left or right to switch between the Cards.
这些卡片是交互图的极好选择，唯一的缺点是它们缺少对象之间的消息如何流动的可视化表示。
These CARDS are an excellent alternative to interaction diagrams, the only drawback being that they lack a visual representation of how messages flow among objects.
卡片切换看起来是要比Apple的程序切换更高效，Apple上切换程序要从屏幕下方加载抽屉，然后再选择程序，确实有些繁琐。
The experience of Card switching looks more efficient than Apple’s current app-switching process, which involves selecting an app from a drawer that loads at the bottom of the screen.
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