Both Apple's Platinum and QNX' PhotonUI revelled in the 3D effects that were a big thing in '90s UI design, but both did so tastefully, using it where it made sense to make elements stand out and to visually separate them from one another. Both of them were also decidedly square and angular, as opposed to the later obsession with rounded corners.
Lastly, and most importantly, both of them were designed in an era where applications were mere means to an end, and users expected - and rightfully so, demanded - that they fit in with the rest of the operating system. This made both of them highly consistent, which I still believe is one of the biggest virtues in UI design, even if the rest of the world no longer cares (in fact, inconsistency seems to have become a goal, not a flaw, since applications need to stand out between the 99.99% of App Store/Play/etc. applications which are utter crap).
Sadly, from the early 2000s onwards, all this was thrown out, and the world was 'blessed' with things like Aqua, Luna, KDE4's Oxygen, Aero, and so on. All of these styles - Aqua and Aero in particular - pretty much ruled the roost, and to this day, Aqua-like and Aero-like themes tend to dominate the popular theme lists for GNOME and KDE.
Still, there's one theme that bucks this trend; a theme which brings the what we now consider 'classic' UI design of the '90s into the modern age, and despite not having seen an update since 2010, has in fact managed to do just that. Christoph Feck's Skulpture for KDE4 manages to bring together classic and modern, arriving somewhere in the middle with something which, while clearly taking you back to those days of Platinum and PhotonUI, still looks entirely modern and fancy. Striking a balance between classic and modern is hard, but Feck nailed it.
The three design principles behind Skulpture tell you all you need to know, really.
- Skulpture has a classical look
Flat gradients are used to oppose the current trend of shiny or "glassy" buttons used in other styles, giving it a conventional classical look that can stand the whole KDE 4 lifetime, if not longer.
- Skulpture is three-dimensional
Light and shadow effects are applied to generate the impression of a three-dimensional user interface, with elements raised out of (and sunken into) the window surface.
- Skulpture is real artwork
Giving it a photo-realistic (antialiased) appearance, pixel-perfect alignment and spacing between user interface elements, this style has been created to please users eyes.
However, none of these design principles are taken to their extremes. Sure, it prefers flat gradients, but it doesn't take it too far. It goes for the 3D look, but the third dimension doesn't overstay its welcome. Less professional themes tend to take things way too far - transparency impeding readability, extreme glossiness causing focus issues, and so on - but Skulpture does it all in moderation.
It's not all roses and sunshine, though. The theme hasn't been updated in almost three years now, and it's starting to show - Kwin changed its shadow system somewhere around KDE 4.7, and as a consequence, the Skulpture Kwin decoration no longer has one, with no way to fix it. You really start to appreciate the importance of window shadows the moment you have to do without.
Still, this may be a blessing in disguise, since in my view, Skulpture's window decoration is clearly its weak point. It doesn't seem to fit with the rest of the style, and the gloss stands out like an eyesore. Because of these two things, you'd do good by opting for a different Kwin decoration.Lastly, it's quite hard to find a proper colour scheme that really makes the most of Skulpture. I've been using Skulpture for years, but only this past week have I finally managed to find just the right scheme, but it took lots of tweaking. Skulpture doesn't like it too light, but it doesn't like it too dark either. Like Skulpture striking a perfect balance between classic and modern, you have to find the perfect balance between light and dark to really make it shine.
In a world full of themes with transparency-up-the-bum and now-with-even-more-gloss, Skulpture stands as a pillar of reason, and offers the answer for those of us with a longing for something to bring the interfaces of the '90s into the modern age. You can get Skulpture through KDE's Get New Stuff, or straight from its own website. There's a 3rd party matching Plasma theme (whoever decided not to unify Plasma with regular KDE styles needs to be point and laughed at) called Atelier as well (which, coincidentally, could also use an update).