Most of what you can change about a Mac screen takes something away. Night Shift takes the blue out of the color. The brightness slider takes light out. Dark Mode takes the glare out of the frame around your windows. A small light in the corner of the screen works the other way around. It puts one warm point of light on the glass and leaves the rest of the picture as it was. It is there for the same reason a small lamp sits on a desk that already has a ceiling light: the desk feels different with it on.
A second, smaller source of light
Ambience is the whole of the job. The light sits in one corner of the display and sways, slowly, the way the light thrown by a small flame moves along a wall. The rest of the screen carries on being a screen. On the Mac App Store, Petit Fire sits under Lifestyle rather than Productivity, which is where a light like this belongs.
Whole-screen settings answer a different question. Night Shift and the brightness slider decide how the entire picture reads late in the day, and they go on deciding that whether or not a corner is lit. A corner light settles something smaller: what sits beside the work while the work happens. If a paragraph is hard to read or a spreadsheet is hard to look at, the built-in settings are where that answer lives.
What is left is the lamp on the already lit desk: a second, smaller source of light. With one corner of the display lit, the screen reads as a surface with a near edge and a far one, rather than as a single flat pane.
The difference between changing a screen and adding to one
Every built-in option changes the screen as a whole. Night Shift retints every pixel. The brightness slider scales every pixel. Reduce Transparency and Dark Mode change how the interface itself is drawn. Even a dimming overlay covers large parts of the display, because the point of an overlay is to darken the frame around your work.
A corner light touches one small area and leaves the rest of the screen alone. Your windows render the same and your colors read the same. If you took a screenshot with that corner out of frame, the light would be absent from the picture. That makes it a different kind of thing from a dimmer, even though both are something drawn over your screen while you work.
The two kinds of change also sit together. A corner light and Night Shift can both be on at eleven at night, each doing its own half: one decides how the whole picture reads at that hour, and the other puts a warm point of light into one corner of it.
What Petit Fire does with that idea
Petit Fire is a small Mac menu bar app built around this one idea. Click the menu bar icon and a warm light appears in a corner of your screen, drawn the way the light from a small flame would fall there. Click the icon again and it goes out. Everything else about the app lives in the menu behind that same icon.
Right-click it and five settings are there: how bright the light is, how large the lit area is, which corner it sits in, how loud the optional sound is, and whether the sound plays at all. The sound is a recording of a wooden-wick candle, and it stays silent until you switch it on. It plays from a different stretch of the recording each time, joined by a crossfade, so what comes around again is the sound itself rather than a fixed interval.
There is also an Open at login setting, which makes the app available when you log in. Lighting it is still the click, as it is at any other time of day.
The light is easier to see on a dark screen. On a bright desktop in daylight it is still there, but faint. Dark Mode, or a dark wallpaper, shows it the way it was meant to be seen. The app runs on macOS 14 or later, and it is free on the Mac App Store.
Choosing the corner, and how bright to leave it
If you try a corner light, start with the corner rather than the brightness. Put it near where your eyes already rest between tasks. On a wide display that is usually a bottom corner, because a gaze drifts down and out more often than up. Behind the paragraph you are reading, the light has to compete with the words, and the setting for place exists so that you can move it in a click when it does.
Then set it lower than your first instinct. At a low setting the light stays out at the edge of the picture while the work stays in the middle. Raise it later from the menu if the corner keeps disappearing into a bright wallpaper.