It was one of the more dramatic U-turns that Microsoft had ever made: undoing the error that was Office Web Apps and providing well-provisioned, fully functional and free versions of the major Office suite applications, first on iPad and later on Android

In fact, Microsoft rolled out the new Office look and feel first on those foreign platforms before dealing with the domestic issue of making Office at home on Windows once again.

Microsoft took the hit for it, waiting until just last February to produce the touchscreen version of Office for tablets that the company had promised back in 2011 for Windows 8. Now that these preview apps are freely downloadable from the Windows Store, desktop PC users everywhere have been wondering how long they have to be stuck driving, if you will, an outdated vehicle.

There is still no final release date, but during the Build 2015 keynote in San Francisco yesterday, developers got their first glimpses of Office 16 (version No. 16 and also, quite likely, 2016) for the classic Win32 desktop platform.

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Clearly, the Office apps are all adopting a similar, though not entirely uniform, style that features solid colors for the title bars, but let’s look beneath the surface a moment:

Microsoft’s hope is that add-ins will be featured more prominently. Ever since Office 2000, it has pushed for a kind of apps ecosystem around third-party functions that run inside of Office apps. With this preview build of Word 16, it’s opening up entire snap-in panes that can be co-opted by third parties — in this case, by document signing service DocuSign.

So far, very little else has changed in Word. A 3 1/2-inch diskette icon still represents “Save,” even though many high school-age users don’t know what the funny square block means.

The most curious addition here is the “touch” button, which appears here as the rightmost button in the Quick Access Toolbar on the left. To date, the Office 2012 desktop applications — particularly Word — have created headaches for tablet users. For instance, they’ll insist on pulling up the on-screen keyboard when a physical one is attached, then when users dismiss the on-screen keyboard, they end up moving the cursor.

This button is an indicator that Microsoft may be applying its “Continuum” design strategy to Office. If this does what such buttons are known to do, it would manually snap the application into (and out of) touch-sensitive mode, where the ribbon buttons would be larger and with more space between them.

(The happy-face icon beside Microsoft CEO Satya Nadella’s smiling face is the “Feedback” button for beta testers, and will not appear in the final edition. Nor will Satya, most likely.)

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The bold title bar colors along the top (reversed from the bold status bar stripe along the bottom in Office 2013) makes PowerPoint stand out dramatically from Word. Here again, rather than demonstrate the product’s functions head-on, Microsoft is demonstrating PowerPoint as a platform for running third-party packages written in HTML5 and JavaScript: in this case, downloadable clip art from an assets library.

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Besides the add-in panes, the changes thus far look strictly cosmetic. Outlook shows the only sign of some user experience tweaking. This demo showed executable tools from Salesforce being sent as an attachment to an Outlook e-mail message, enabling third-party functionality without the need for a separate pane.

If you look closely here, though, notice Outlook has added a buttons bar along the right side for frequently used commands, like Reply, Next and Delete. There’s a New Mail button added to the top of the Navigation pane on the left side.

But besides the fancy new wallpaper, where’s the value-add? Is there a reason for Office 2012 users to upgrade?

If there is a single compelling reason (besides wanting to have Office look as pretty as it does on your iPad), it will have to come from Microsoft’s biggest gamble yet in opening up access to people’s everyday work: a new, open API that lets an application (a Web app, or perhaps a macro inside Office) see what other users are working on, and maybe respond with something useful.

Clearly, this “Office graph” data, as it may eventually be called, will only be made visible through the desktop apps. However, if developers learn how to take advantage of it, and if security for these data exchanges actually works, then this could be the game changer that rebuilds Office 2016 into the collaboration platform that Google Apps has failed to become.

Nadella gave his blessing to yesterday’s news by bestowing one of his now-classic run-on sentences.

“This fundamental platform shift of Office, where the one billion-plus users of Office are available to you as developers; the semantically rich graph that is available for you to consume and extend, and to drive additional engagement through intelligence, we believe is going to change the very fundamental nature of what Office is, to becoming really a platform from us and from you together,” Nadella said. Two fundamentals in one sentence.