After installing the Google Play Music app, the first screen allows you to choose which Google account to associate with it.
Seems straightforward enough; but have a look at the screen - what you would press?
Looks like there's a choice of two commands, either Add account or Not now. But there's another command there ... the email address is a clickable hyperlink, but there's no indication that it is - no underline or radically different font. The Add account button actually prompts you to type in a new email address, i.e. not the one listed. One of the most confusing UI designs I've seen lately.
As discussed in this StackExchange.UX post, there's no strict rule about it, but buttons usually perform a command and hyperlinks usually take you somewhere new.
To improve it, maybe there should be a "Use" button to the right of each email address.
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