Foundations
Light and depth
One lamp, high and to the left. Everything is raised, level or recessed, and a pressed part sits below the plate.
Four heights
Every part is at one of four heights relative to the plate. The drawing is a section through each; above it, the part itself, live.
The lamp is always above left. Highlights go on top and left edges; shadows fall down and to the right. A shadow that falls up, or a highlight on a lower edge, is a bug.
Pressing
A key is a cap on a skirt. Pressed or latched, it moves down by exactly the skirt and swaps its shadows for the pressed set: a shadow inside the top edge, a little on each side, and a lit line below where the plate’s lip shows. A latched selector key, a checked check and a checked radio do the same. A pressed state that only darkens, or only draws an outline, is not pressed.
The light never turns
Turn this knob. The ridges and the pointer rotate; the highlight on the cap and every shadow stay exactly where they are, because the lamp did not move. Anything new that rotates must split the same way.
No glow, no frost
Only lamps and lit displays glow. There is no blurred glass as a material and no frosted card: the only glass in the kit is a display.
The full law
This page is a summary in plain words. The brain holds the law itself, written for an agent to follow.
The full law, with the foundations they rest on and the anti-patterns that break them. Full rules ship in the brain with the Pass.