Display glasses web apps, simulated in your browser

Pure black emits nothing, so it arrives as clear glass. The card you drew does not exist on the glasses: only the marks you lit up do. This is why a design that looks composed on a monitor arrives as loose text floating over traffic. Draw the container in a dark grey that still emits, or accept that there is no container.

A pixel has no size on glasses. The panel floats about a metre away and subtends a fixed angle, so the only honest unit is how much of the wearer's vision a letter occupies. Roughly 0.6 degrees is the floor for legibility, and anything you expect read at a glance, in motion, should sit well above it.

On Meta Ray-Ban Display that arithmetic is fixed: 20 degrees across a 600 pixel grid, so one degree is 30 authored pixels. The simulator prints the angle your current size works out to, live, next to the size slider.

On a monitor, contrast is a property of two colours you chose. Here it is a property of the light falling on the wearer's face, which you do not control and cannot predict. The same layout is crisp in a library and gone on a forecourt at noon.

So there is no such thing as a design that passes. There is only a design and the illuminance it stops working at. Find that number and decide whether you can live with it.

Saturated colour is dim colour: a pure red is one channel doing all the work, and one channel cannot out-shout daylight. Cyan, green and near white carry two or three channels, which is why they survive. Deep blue is the worst case on almost every combiner.

Which breaks the usual convention, because red is what you reach for to say stop. On glasses red says nothing at all outdoors. Carry the urgency with size, motion or position instead.

A drop shadow is a subtraction: it works by taking light away from what is behind it. An additive display has no way to take anything away, so a shadow is simply not rendered. Every elevation cue built on shadow is invisible here.

Build hierarchy the other way round. A dark but non-black surface with a brighter edge reads as a seat for content, and the difference between two levels becomes a difference in emitted light rather than in cast darkness.

A notification on a phone competes with a screen the user is already looking at. A notification on glasses competes with the road. Anything that snaps into place pulls focus from the world whether or not it deserved to, and the wearer has to physically refocus about a metre out to answer it.

Let information arrive over roughly two seconds so it can be noticed and declined without a decision. Keep instant response for direct feedback only: a focus ring, a selection, anything the wearer just caused.

The real budget is not the 600 by 450 grid. It is about one second of attention, taken off-axis, usually while walking. Whatever cannot be understood in that second is not slow, it is absent.

In practice this means one number and one label. If a second idea genuinely has to be there, it belongs on the next screen, not the next line.