For a few years there, it felt like major changes in OS X's look and behavior were imminent. The conventional wisdom during the Lion and Mountain Lion eras was that Apple had placed OS X on a collision course with iOS, and inevitably the two would come together to form...well, if not a single operating system, then two variations on a single theme.

In the past year, though, it's become clear that Apple no longer believes in that approach, if it ever truly did. iOS 7 took big, bold steps in one direction--and OS X Yosemite takes smaller steps in a different one. After spending several days running Yosemite (on a Retina MacBook Pro provided to me by Apple and pre-loaded with the first developer release), it's clear that Apple has a very clear and distinct future in mind for the Mac--even though some of today's Apple hardware might not be up to delivering it.

The year of Retina

During 2012's WWDC, Apple unveiled the 15-inch MacBook Pro with Retina display, and a few months later the 13-inch models arrived. But two years into the Retina Mac era, there are still no Retina iMacs or MacBook Airs, nor are there affordable external Retina displays.

For a while now, I've thought that 2014 would be the year that Retina spreads across the Mac product line. After spending time with Yosemite on both Retina and non-Retina systems, I'm more confident than ever in that guess. Yosemite's new design feels like it was built for Retina displays: Thin Helvetica Neue replaces the long-serving but chunky Lucida Grande as the system typeface. Transparency is more present than ever before, inside app windows and underneath toolbars and even on the login screen itself.

There's no doubt that within a few years, most Mac users will be using high-resolution displays. That's the direction Apple is heading in, and while it will take longer to happen than it did in smartphones and tablets, it will happen. And three-quarters of the Macs Apple sells are laptops. As a result, it's a wise decision for Apple to consider, say, the 13-inch Retina MacBook Pro as the reference Mac for design purposes.

OS X Yosemite is gorgeous on such a display. So here's hoping Apple rolls out high-resolution iMacs, MacBook Airs, and (dare I hope?) an external display later this year; if it does, Yosemite's refined look will be able to shine up and down the product line.

Beyond the system font, the most obvious visual change in Yosemite is that the gray light-to-dark gradient atop most windows is now a single gray tone. In addition, the red, yellow, and green "stoplight" buttons on the corners of windows--the ones you use to close, minimize, or zoom that window--have been stripped of the shading effects that made them look like pieces of candy. They're just flat circles now. (When you move your cursor over them, you'll find the same X in the red circle and minus-sign in the yellow circle. The green circle no longer displays a plus-sign, however; instead, it shows the two-headed arrow that indicates full-screen mode. If you want to zoom a window's size in and out, old-school style, you'll now need to hold down the Option key before clicking the green button, or just double-click on the window's title bar.)

Apple showed off a new "dark mode" for the OS X interface when it previewed Yosemite at WWDC. Unfortunately, the build of Yosemite I received didn't implement this feature. I'm looking forward to seeing what OS X feels like when it switches to light text on a dark background.

Embracing wide and small screens

Just about every Mac uses a display that's a lot wider than it is tall. So in the Mac interface, height is at a premium, while there's width to spare. (This is why I don't understand why people leave their Dock visible on the bottom of the screen--I've always pinned mine to the right side.) Yosemite's design tries to fit more stuff on your screen by cutting the height of many window title bars in half.

This has a ripple effect on other interface elements. Take, for example, those stoplight buttons that were previously on the same level as the centered name of the window and, far off to the left, the double-headed arrow icon for full-screen mode. Now those buttons share space at top of windows with other interface elements.

In Yosemite's version of Safari, the three buttons are on the same level as toolbar elements such as the next/previous page button, the address/search bar, and the like. In fact, in Safari the name of the window (and, therefore, the title of the page you're viewing) is completely gone.

In Contacts, meanwhile, the entire top window bar is gone. The stoplight buttons still remain at the top-left corner of the window, but that's now at the top of the leftmost visible pane of the application. They hover over the translucent Groups column until you choose View > Hide Groups, at which point they hop over to the top of the Contacts column (which turns from white to translucent in the process). A thin band across the top of the Contacts window is still draggable, but it's not what you'd call a traditional Mac title bar.

This design isn't consistent across all of Apple's apps, either. (Since this is an early developer-preview edition, things could certainly change before Yosemite reaches users this fall.) The stoplight buttons share space with the toolbar in the Calendar, Maps, Messages, and Reminders apps. (Philosophical question: If a bar contains no title, can it still be called a title bar?) Yet Mail, TextEdit, Preview, and iWork all look the same as they ever did.

I don't really mind the trend--I use an 11-inch MacBook Air every day, so I know about cramped working environments. By merging the toolbar and title bar, this approach saves some precious vertical space. Unfortunately, an overly cluttered title bar might be hard to reposition on screen if you can't find anywhere to click that isn't covered by a button. And while those old title bars featured an awful lot of empty space, sometimes such space can be good. Yosemite's new look can lead to situations where windows feel more cluttered.

I have to admit I'm also a little nonplussed about the disappearance of titles from the top of many windows. In apps that never really have more than one important window (Calendar and Maps come to mind), the title is unnecessary; labeling my Calendar window with the word Calendar seems pointless. But in many other contexts, the title of the window imparts important information, and there's a danger that some of that information could be lost if Apple takes this approach too far. It's something worth keeping an eye on, especially given the radical changes Yosemite has in store for Safari. (More on that in a future installment of this series.)

More subtle changes

As with most OS X releases, Yosemite has its share of subtle design changes. The most notable is probably the system's increased use of translucency, in which some interface elements are semi-opaque, allowing a blurred-out version of whatever is behind the window to show through. It's a style iOS 7 uses in abundance, and it's now sprinkled here and there in Yosemite. The Messages sidebar, for instance, is translucent. It's subtle, so it doesn't harm readability, but it doesn't really seem to serve any useful purpose. It's a light design flourish that isn't offensive, but it's not particularly bold either.

Up in the (still translucent) menu bar, the bars on the Wi-Fi icon are thinner, and a simplified battery icon on laptops feels more like the one from iOS. The Spotlight menu bar item remains anchored next to the similarly immovable Notification Center icon, despite the fact that the Spotlight window itself now floats in the center of the screen. I sense a disconnect here.

Beyond the occasional window pane, translucency effects pop up in a few other places in the system. When Exposé is triggered, the background now fuzzes out, and there's a similar effect on the login screen, which shows a fuzzed-out picture of Half Dome.

Several other interface elements have been flattened in the same style as the stoplight buttons, as well. Most notably, the pulsating blue glass-textured button in dialog boxes has lost its texture (the glass texture that still remained from OS X's "aqua" interface is gone), it's darker (with the text in white), and it doesn't pulsate anymore.

Apple's engineers have taken a trip to The Container Store, and the result is that the system's trash can is now a white translucent plastic job rather than the metallic wire basket previously favored. (Oscar the Grouch demands a return of the big metal trash can from the classic Mac OS, but nobody listens to smelly muppets.)

And the Dock, which in recent versions of the OS had become a 3-D shelf at the bottom of your screen upon which your icons sat, has reverted to something simpler. Like the Dock that you can still find in Mavericks if you set it to display on the left or right side of your screen, Yosemite's dock is merely a 2-D background with a hint of translucency. It's a great improvement, but seriously folks, consider pinning your Dock to the left or the right side. (Try it, you'll like it!) The subtle glow beneath running applications in the Dock is now a more noticeable black dot.

There's also a fresh new face in OS X Yosemite--literally. The "Mac face" logo that has represented various portions of the Mac (originally Mac OS 8, most recently the Finder) for the last sixteen years, has been updated. The image (actually two faces, one with two eyes viewed face-on half comprised of the profile of a different face) still represents the Finder, but it's been tweaked. Farewell, old face, you served us well.

Finally, this breaking news from the System Preferences app: The compact fluorescent light bulb that represented the Energy Saver preference pane since 2008 is no more. After visiting The Container Store, Apple's OS X elves popped into The Home Depot and picked up an LED light bulb. (I assume Oscar the Grouch is still lamenting the loss of the incandescent bulb.)

Skin deep

The design changes in Yosemite are noticeable, but the system is still very recognizably OS X. Longtime Mac users' fears that the Mac was about to collide with iOS in some kind of crazy peanut butter-chocolate disaster have not been borne out. It's a forward-thinking design that looks better on Retina displays, pointing the way toward a high-resolution future for Mac users.

Some of the design decisions in this first developer release seem a little unfinished, which is fair enough--the OS itself is unfinished! I'd like to see more consistency when it comes to the way stoplight buttons and title bars are displayed, and I worry about the increased clutter and decrease in clickable areas for dragging windows. I'm also a bit concerned about the loss of window titles in apps where they impart real information. It'll be interesting to see how Apple designs its individual built-in apps, and what decisions third-party Mac developers make on this front.

But otherwise, there's a lot to like in Yosemite's design. Unless, perhaps, you're Oscar the Grouch.