@andrew84 , yes, I also have this picture, but only after 3 seconds.
Everything is the same as without this key.

@andrew84

no, I checked on different browsers on Chromium. This flag is only available at Opera. And it doesn't work.

This whole story looks even more stupid, when I see that one designer has darkened the entire window, and another designer has highlighted a button , rather than killing the picture.

But they do not know about each other, although they work in neighboring offices.

This back for button drawn so simply:
boreder-radius: 50%;
background-color: #0008;

Imagine that in the same way, in 1 line code, the entire window is darkened.
One a string of code , that users have been asking to remove for 5 years.
There is no need to invite a team of developers, develop new engines, or master new technologies. Just remove 1 line of code - someone's old mistake. Perhaps that designer is no longer on the team. But his mistake lives on.
Because developers don't read their forum.

Try searching the video for the right moment. You show me progress bar (s), and I need the video itself, every pixel of it. And I will find the progress bar on my own.

It's PIP. So I can use the main browser window to work. I can accidentally carry a mouse over a PIP. Hundreds of times a day. I call this PIP a traffic light - I have so many negative emotions from this flashing. And all for buttons that I don't need.

By the way, Youtube himself does not care much about his users - and no one has complained yet. On Shorts, white text on the video: channel name, tags, music does not stand out at all. And everything is fine. If the text is not visible, wait 1 second - and the video will change. No need for big white buttons (everyone already knows their purpose, placement) there is no need to spoil the video itself.

2. We are on desktop - what does the pause button do in the center of the screen???

I’ll tell you a secret - In the center of the screen there is a person’s face, eyes, his nose, text, program code. Anything. But browser buttons always look very inappropriate there.
Remove these buttons from the center - I don’t have fingers with which I will poke at the FullHD center.

I can copy pictures from there. It is clearly visible that YouTube approached the issue less clumsily. Google knows what a linear gradient is. Everything is solved in 1 line of code.

Do you see on that forum the only user who proposed a ready-made solution, I with a beautiful "banned" tag? It's me. I bow low. There, the Vivaldi moderators (who themselves do not know this CSS) appreciated my proposal.

I know that many users have looked at browser code looking for this PIP to remove it themselves.
I looked too, but found nothing. So, this is a serious problem, an unnecessary solution that prevents us from living.

Here's the simplest gradient I came up with. And it will solve the problem of invisible buttons. And this is approximately how the Youtube-player works.

linear-gradient(to bottom, transparent 90%, rgba(0, 0, 0, 0.3) 100%)

There is a similar topic on the forum of another browser.
For at least 5 years, users have been asking developers to remove the PIP darkening under the mouse.
Do I want to ask you: Why darken an entire window? For one button in the center? It takes up 1%, but you darken all the other 99%. I personally don’t need this 1% - I can look at these buttons without your help.
Video (where the screen is completely white (where one button may not be visible), exactly 0.000001% relative to all other videos. There are no completely white videos. I don't know how to convince you. Again, you darken 99.999999 % of the video, where the center button is perfectly visible in the video itself, without CSS help.

@zeonish коллега, я немного знаком с языками.

Отступы: да , многовато, но не критично. Ты видел ARC ? Умнож эти отступы на 2.

Закругление: Даже не твоем скрине видно, border-radius: 3px ; Не 10, не 30, а 3-4px.
Это отлично.

Шрифт да, мелковат. Cтандартный Arial .Но спасибо, что не New Times. И то хорошо,

Обидно, что все это настраиваетсяя буквально в 2 строки кода.
Других обвинений ты не привел .

Я восхищался сложностью интерфейса . Все асболюно браузеры используют стандартную среду разработки, только галочки ставь. Это колхоз из прошлых веков. Opera GX сделана мощно. Похоже, они весь инерфейс настроек писали с нуля. На голову выше всех остальных.

@zeonish а что не так в интерфейсе ? Я когда первый раз открыл Opera GX , тогда и понял, как должен выглядеть браузер будущего. А с выходом новой Opera One -- такие же впечатления.
Хоть я и не любитель украшений, но я вижу огромную работы авторов.