You'll poke your eye out.

The pillow UI

Be the change you want in the world, there is probably some KDE theming option that'll give you the look you desire.

...oh and I just came to the realization there is probably a way to make a SNES like UI and now it's time to research...

Actually, I don’t hate it. I imagine they would be useful in a touch first UI and as snapping handles regardless. They might be a little big as presented but I could actually see this working, especially as titlebar dragging space has been encroached upon by tabs and menus and such.

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  𝒴ℴ𝓊𝓇 𝓅ℴ𝓈𝓉𝓈 𝒸ℴ𝓊𝓁𝒹 𝓁ℴℴ𝓀 𝓁𝒾𝓀ℯ 𝓉𝒽𝒾𝓈
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Where did our civilization go wrong?

I prefer this over rounded corners

That looks like it would not pass the CE safety certifications here in Europe anyway.

Corners should have spikes and other windows should close upon touching them!

It makes me think of Asian culture in Western comics for some reason.

That's actually a lit idea and I'm going to make note of that for when I eventually launch my comics website which has been delayed multiple years due to competing uses of my and my collaborators' time.

Windows XP UI, where everything looked like a plastic children's toy.

To this day, I really love Windows Phone 7 - 8.1 visual and UX design. Very rectangle, love it. It's the best for mobile IMO. We should go back to when MS can still seem competent enough.

And circles! Why aren't they putting everything in circles on a webpage?

I want to bleed when I use my iPad.