The 20-20-20 rule only works if the screen stops fighting you

Every guide to eye strain says the same thing: every 20 minutes, look at something 20 feet away for 20 seconds. It is good advice and almost nobody follows it. When we asked 40 people to try, the same sentence came back in different words: "I forgot."

So we stopped treating it as a discipline problem and started measuring the screen instead.

What the measurements showed

We logged the intensity setting and page brightness across 40 sessions of continuous reading. Two patterns held every time:

• People who left intensity at 0% stopped reading sooner and adjusted their screen brightness upward within the first ten minutes.
• People who set 30–45% read for longer without touching anything else.

The reason is contrast, not colour. A page of #000 on #fff at full screen brightness is the equivalent of reading a book under a desk lamp pointed straight at the paper. Warmth helps, but the bigger lever is how hard the boundary between text and background is.

Why we removed the Apply button

Early builds had one, and it was the single most-complained-about control in the extension. People would set an intensity, hit Apply, decide it was too strong, and then not know how to get back.

Now the change is live as you drag the slider. That works only because the effect is non-destructive: it is a layer, it does not edit the page, and turning it off restores the original rendering exactly. If we ever add a preset that writes to the page, it gets an Apply button and a confirmation — this rule is about the mechanism, not about taste.

The settings worth copying

• Reading long text in a bright room: eye-care preset, 35%.
• Late night, one more chapter: eye-care at 60%, then a dark preset at 90% if the site already has a dark mode.
• Screenshots and screen shares: turn Turan off for the tab. A tinted screenshot looks like a rendering bug to whoever receives it.

What to do when a site still hurts

Some sites set their own text colour per element and ignore inheritance. The per-site switch in the popup footer turns Turan off for that host entirely. Before you do that, try raising intensity instead: below about 20%, a site with aggressive inline styles will look untouched simply because the layer is too subtle to win.

If a specific host still fails at 80%, send us the URL from the feedback page. Known-bad hosts get site-level fixes in patches, and the list is short enough that we still read every report.