Only discuss dark mode in coding, there are so many famous dark themes, but most of them are not suitable for use at night, for instance: nord, dracula, vscode's github dark, vscode's github dimmed dark(but it is perfect in the github's website, some key differences between them), all vscode's built-in dark themes and so on.
They're terrible, because they use very bright colors for highlight or improper contrast or author's aesthetics:
1. The bright color in dark mode just like a car coming to you in the dark stabbing your eyes with its huge headlights.
2. The improper contrast may be that they do not turn on the lights at night?
3. The essence of code is text, the readability of text is always the first, aesthetics is secondary, the nord theme is elegant and clean, I like it but I will never use it for reading or coding.
Dark mode is not intended for you to use in a purely dark environment, we need light at night even if you don't believe in god.
Here are some positive examples: "Atom One Dark Theme" and "Solarized Dark Vim" in vscode, jetbrains Darcula(not dracula, which is the object of criticism above).
So before answering the question of the title, we need to think: What should a correctly implemented dark mode look like?