/* ==========================================================================
   message-test — shared stylesheet
   Direction: instrument front panel. Cold aluminium face, silkscreened
   legends, inset near-black readout windows with an amber trace, a threshold
   scale used everywhere a number has a pass mark, diagonal hatching for the
   region an instrument refuses to measure.
   Mobile-first: base styles target ~360px, complexity added at 640/768/1024.
   Spacing uses logical properties throughout so RTL mirrors, not just text.
   ========================================================================== */

:root {
  /* Panel */
  --panel:    #d7dcdd;
  --panel-2:  #c6cdcf;
  --panel-3:  #e8ebeb;
  --rule:     #a6b0b2;
  --hair:     #bcc4c5;

  /* Ink */
  --ink:      #10171a;
  --graphite: #4a565a;

  /* Readout window */
  --window:   #0c1214;
  --window-2: #162024;
  --glass:    #93a3a6;

  /* Semantics */
  --trace:    #ffa42b;   /* the measured value */
  --pass:     #0b5f57;   /* at or above the mark */
  --fail:     #9c3019;   /* below it, or out of scope */

  --font-display: "Saira", "Helvetica Neue", Arial, sans-serif;
  --font-body:    "Public Sans", "Helvetica Neue", Arial, sans-serif;
  --font-data:    "DM Mono", ui-monospace, "SF Mono", Menlo, monospace;
  --font-mono:    "DM Mono", ui-monospace, "SF Mono", Menlo, monospace;

  --step--2: 0.75rem;
  --step--1: 0.875rem;
  --step-0:  1rem;
  --step-1:  1.125rem;
  --step-2:  1.375rem;
  --step-3:  1.75rem;
  --step-4:  2.125rem;

  --gap:     1.25rem;
  --pad:     1.1rem;
  --measure: 36rem;

  --hatch: repeating-linear-gradient(45deg,
            rgba(156, 48, 25, .16) 0 5px,
            rgba(156, 48, 25, 0) 5px 11px);
}

[dir="rtl"] {
  --font-display: "Vazirmatn", "Segoe UI", Tahoma, sans-serif;
  --font-body:    "Vazirmatn", "Segoe UI", Tahoma, sans-serif;
  --font-data:    "Vazirmatn", "Segoe UI", Tahoma, sans-serif;
  --hatch: repeating-linear-gradient(-45deg,
            rgba(156, 48, 25, .16) 0 5px,
            rgba(156, 48, 25, 0) 5px 11px);
}

*, *::before, *::after { box-sizing: border-box; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--panel);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--step-0);
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

[dir="rtl"] body { line-height: 1.85; }

img, svg { max-width: 100%; height: auto; }

/* Links: ink text, amber rule beneath. The amber never carries meaning on
   its own, so it never has to pass a contrast check as text. */
a {
  color: var(--ink);
  text-decoration-line: underline;
  text-decoration-color: var(--trace);
  text-decoration-thickness: 2px;
  text-underline-offset: 0.2em;
}
a:hover { background: rgba(255, 164, 43, .28); }
a:focus-visible {
  outline: 2px solid var(--ink);
  outline-offset: 2px;
  background: rgba(255, 164, 43, .28);
}

h1, h2, h3 {
  font-family: var(--font-display);
  margin: 0;
  line-height: 1.14;
  letter-spacing: -0.01em;
}
h1 { font-size: var(--step-4); font-weight: 600; }
h2 { font-size: var(--step-3); font-weight: 600; }
h3 { font-size: var(--step-1); font-weight: 600; line-height: 1.3; }
[dir="rtl"] h1, [dir="rtl"] h2, [dir="rtl"] h3 { letter-spacing: 0; line-height: 1.4; }

p { margin: 0 0 1em; max-width: var(--measure); }
p:last-child { margin-block-end: 0; }

ul, ol { max-width: var(--measure); }

.skip {
  position: absolute;
  inset-inline-start: -9999px;
  inset-block-start: 0;
  background: var(--ink);
  color: var(--panel-3);
  padding: .8rem 1rem;
  z-index: 50;
}
.skip:focus { inset-inline-start: 0; }

.wrap {
  inline-size: 100%;
  max-inline-size: 62rem;
  margin-inline: auto;
  padding-inline: var(--pad);
}

/* ── Header ─────────────────────────────────────────────────────────────── */

.site-head {
  background: var(--panel-2);
  border-block-end: 1px solid var(--rule);
  position: sticky;
  inset-block-start: 0;
  z-index: 20;
}
.site-head .wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem 1rem;
  min-block-size: 56px;
  padding-block: .5rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: .55rem;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: var(--step-0);
  letter-spacing: .01em;
  text-decoration: none;
  padding-block: .55rem;
  min-block-size: 44px;
}
.brand:hover { background: none; text-decoration: underline; text-decoration-color: var(--trace); }

.lang-switch {
  margin-inline-start: auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-block-size: 44px;
  min-inline-size: 44px;
  padding-inline: .85rem;
  border: 1px solid var(--rule);
  background: var(--panel-3);
  font-family: var(--font-data);
  font-size: var(--step--1);
  text-decoration: none;
}
.lang-switch:hover { background: var(--trace); }

.nav { flex-basis: 100%; }
.nav ul {
  display: flex;
  flex-wrap: wrap;
  gap: 0 1.1rem;
  list-style: none;
  margin: 0;
  padding: 0;
  max-inline-size: none;
  border-block-start: 1px solid var(--hair);
}
.nav a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-block-size: 44px;
  min-inline-size: 44px;
  font-family: var(--font-data);
  font-size: var(--step--1);
  text-decoration: none;
  color: var(--graphite);
}
.nav a:hover, .nav a:focus-visible { color: var(--ink); background: none; box-shadow: inset 0 -3px 0 var(--trace); }

/* ── Shared bits ────────────────────────────────────────────────────────── */

.eyebrow {
  font-family: var(--font-data);
  font-size: var(--step--2);
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--graphite);
  margin: 0 0 .9rem;
}
[dir="rtl"] .eyebrow { letter-spacing: 0; text-transform: none; font-size: var(--step--1); }

.lede {
  font-size: var(--step-1);
  line-height: 1.55;
  max-inline-size: 34rem;
}
[dir="rtl"] .lede { line-height: 1.9; }

.note {
  font-size: var(--step--1);
  color: var(--graphite);
}

/* ── Hero ───────────────────────────────────────────────────────────────── */

.hero { padding-block: 2.25rem 1.75rem; }
.hero h1 { margin-block-end: .9rem; text-wrap: balance; }

/* ── Readout window ─────────────────────────────────────────────────────── */

.readout {
  background: var(--window);
  color: var(--glass);
  border: 1px solid var(--ink);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, .07);
  padding: .95rem .9rem 1.1rem;
  margin-block: 1.6rem;
  font-family: var(--font-data);
  font-size: var(--step--1);
  line-height: 1.5;
  --scale-track: #263236;
  --scale-thr: #e8ebeb;
}
.readout a { color: var(--trace); text-decoration-color: var(--trace); }
.readout a:hover { background: rgba(255, 164, 43, .2); }

.readout__bar {
  display: flex;
  flex-wrap: wrap;
  gap: .25rem .8rem;
  padding-block-end: .7rem;
  margin-block-end: .9rem;
  border-block-end: 1px solid #263236;
  font-size: var(--step--2);
  letter-spacing: .06em;
  text-transform: uppercase;
  color: #6f8085;
}
[dir="rtl"] .readout__bar { letter-spacing: 0; text-transform: none; }
.lit { text-transform: none; letter-spacing: 0; }

.row { margin-block-end: .95rem; }
.row:last-child { margin-block-end: 0; }

.row__top {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: .2rem .7rem;
}
.row__label {
  font-size: var(--step--2);
  letter-spacing: .14em;
  text-transform: uppercase;
  color: #7d8f94;
}
[dir="rtl"] .row__label { letter-spacing: 0; text-transform: none; font-size: var(--step--1); }

.row__val {
  font-family: var(--font-data);
  font-size: var(--step-2);
  font-weight: 500;
  color: var(--trace);
  line-height: 1.1;
}
.row__val small { font-size: var(--step--1); color: #7d8f94; }

.row__sub {
  margin: .35rem 0 0;
  max-inline-size: none;
  font-size: var(--step--1);
  color: #7d8f94;
}

.row__verdict {
  font-size: var(--step--2);
  letter-spacing: .12em;
  text-transform: uppercase;
  padding: .18rem .45rem;
  border: 1px solid currentColor;
}
[dir="rtl"] .row__verdict { letter-spacing: 0; text-transform: none; }
.is-below { color: #ff7a5c; }
.is-above { color: #5fd0be; }
.is-skipped { color: #7d8f94; }

.row__gloss { margin: .45rem 0 0; color: #93a3a6; max-inline-size: none; }

/* ── The threshold scale: the page's signature device ───────────────────── */

.scale { margin-block-start: .55rem; }
.scale__track {
  position: relative;
  block-size: 12px;
  background: var(--scale-track, var(--panel-2));
  border: 1px solid rgba(0, 0, 0, .18);
}
.scale__fill {
  position: absolute;
  inset-block: 0;
  inset-inline-start: 0;
  inline-size: var(--v, 0%);
  background: var(--trace);
}
/* The band an instrument accepts. Narrow for the clarity index, wide for
   the cloze test, and the width of the band is the point. */
.scale__zone {
  position: absolute;
  inset-block: 0;
  inset-inline-start: var(--t, 50%);
  inline-size: calc(100% - var(--t, 50%));
  background: var(--pass);
}
.scale__thr {
  position: absolute;
  inset-block: -5px;
  inset-inline-start: var(--t, 50%);
  inline-size: 2px;
  background: var(--scale-thr, var(--ink));
}
.scale__marks {
  display: flex;
  justify-content: space-between;
  font-family: var(--font-data);
  font-size: var(--step--2);
  color: inherit;
  opacity: .8;
  margin-block-start: .5rem;
}

.scale--light {
  --scale-track: #b7c0c2;
  --scale-thr: var(--ink);
}
.scale--light .scale__marks { color: var(--graphite); }

@media (prefers-reduced-motion: no-preference) {
  .scale__fill { animation: settle 1s cubic-bezier(.16, .84, .3, 1) both; }
  @keyframes settle { from { inline-size: 0; } to { inline-size: var(--v, 0%); } }
}

/* ── Buttons ────────────────────────────────────────────────────────────── */

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: .7rem;
  margin-block-start: 1.5rem;
}
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-block-size: 48px;
  padding-inline: 1.15rem;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: var(--step-0);
  text-decoration: none;
  border: 1px solid var(--ink);
  flex: 1 1 auto;
}
.btn:hover { background: none; }
.btn--solid { background: var(--ink); color: var(--panel-3); }
.btn--solid:hover { background: var(--window-2); box-shadow: inset 0 -4px 0 var(--trace); }
.btn--ghost { background: transparent; color: var(--ink); }
.btn--ghost:hover { box-shadow: inset 0 -4px 0 var(--trace); }

/* ── Module: a plate on the panel with a silkscreened legend ────────────── */

.module {
  position: relative;
  background: var(--panel-3);
  border: 1px solid var(--rule);
  padding: 2.4rem .95rem 1.5rem;
  margin-block: 1.75rem;
}
.module__legend {
  position: absolute;
  inset-block-start: 0;
  inset-inline-start: 0;
  background: var(--ink);
  color: var(--panel-3);
  font-family: var(--font-data);
  font-size: var(--step--2);
  letter-spacing: .16em;
  text-transform: uppercase;
  padding: .4rem .65rem;
}
[dir="rtl"] .module__legend { letter-spacing: 0; text-transform: none; }
.module > h2 { margin-block-end: .8rem; text-wrap: balance; }

/* ── Instruments ────────────────────────────────────────────────────────── */

.instruments { list-style: none; margin: 1.5rem 0 0; padding: 0; max-inline-size: none; }
.instr {
  border: 1px solid var(--rule);
  background: var(--panel);
  padding: 1rem .9rem 1.1rem;
  margin-block-end: 1.1rem;
}
.instr:last-child { margin-block-end: 0; }
.instr h3 { margin-block-end: .15rem; }

.instr__cost {
  font-family: var(--font-data);
  font-size: var(--step--2);
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--graphite);
  margin: 0 0 .8rem;
}
[dir="rtl"] .instr__cost { letter-spacing: 0; text-transform: none; font-size: var(--step--1); }

.instr__gauge {
  border-block: 1px solid var(--hair);
  padding-block: .8rem;
  margin-block: .9rem;
}
.instr__gauge p { margin: 0 0 .5rem; font-size: var(--step--1); }

.instr__limit {
  font-size: var(--step--1);
  color: var(--graphite);
  border-inline-start: 3px solid var(--fail);
  padding-inline-start: .7rem;
  margin: 0;
}

/* ── Interlock: the one thing this page is loudest about ────────────────── */

.interlock {
  background: var(--window);
  color: #c6d1d3;
  border: 2px solid var(--fail);
  margin-block: 2rem;
}
.interlock__plate {
  background: var(--fail);
  color: #fff;
  font-family: var(--font-data);
  font-size: var(--step--2);
  letter-spacing: .2em;
  text-transform: uppercase;
  padding: .5rem .9rem;
  display: flex;
  align-items: center;
  gap: .55rem;
}
[dir="rtl"] .interlock__plate { letter-spacing: 0; text-transform: none; font-size: var(--step--1); }
.interlock__body {
  padding: 1.1rem .9rem 1.3rem;
  background-image: var(--hatch);
}
.interlock h2 {
  font-size: var(--step-2);
  color: #fff;
  margin-block-end: .8rem;
  text-wrap: balance;
}
.interlock p { color: #c6d1d3; }
.interlock strong { color: #fff; }

.interlock__ledger {
  list-style: none;
  margin: 1.1rem 0 0;
  padding: 0;
  border-block-start: 1px solid #2c3a3e;
  font-family: var(--font-data);
  font-size: var(--step--1);
}
.interlock__ledger li {
  display: flex;
  gap: .6rem;
  padding-block: .55rem;
  border-block-end: 1px solid #2c3a3e;
}
.interlock__ledger b { color: #5fd0be; font-weight: 500; flex: 0 0 auto; }
.interlock__ledger .no { color: #ff7a5c; }

/* ── Rules list ─────────────────────────────────────────────────────────── */

.rules { list-style: none; margin: 1.3rem 0 0; padding: 0; max-inline-size: none; }
.rules li {
  border-block-start: 1px solid var(--hair);
  padding-block: 1rem;
}
.rules li:last-child { border-block-end: 1px solid var(--hair); }
.rules h3 { margin-block-end: .35rem; }
.rules p { font-size: var(--step--1); }

/* ── Steps ──────────────────────────────────────────────────────────────── */

.steps { list-style: none; margin: 1.3rem 0 0; padding: 0; counter-reset: none; max-inline-size: none; }
.steps > li {
  display: grid;
  grid-template-columns: 2.1rem 1fr;
  gap: .1rem .8rem;
  padding-block: .95rem;
  border-block-start: 1px solid var(--hair);
}
.steps > li:last-child { border-block-end: 1px solid var(--hair); }
.step__n {
  grid-row: span 2;
  font-family: var(--font-data);
  font-size: var(--step-1);
  color: var(--fail);
  line-height: 1.25;
}
.steps h3 { font-size: var(--step-0); }
.steps p { font-size: var(--step--1); margin: .2rem 0 0; }

/* ── Code ───────────────────────────────────────────────────────────────── */

.code {
  background: var(--window);
  color: #d3dcde;
  border: 1px solid var(--ink);
  padding: .85rem .8rem;
  margin: 1.1rem 0 0;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: var(--step--1);
  line-height: 1.9;
  direction: ltr;
  text-align: start;
}
.code b { color: var(--trace); font-weight: 400; }
.code .cmt { color: #6f8085; }

/* ── References ─────────────────────────────────────────────────────────── */

.refs { list-style: none; margin: 1.3rem 0 0; padding: 0; max-inline-size: none; }
.refs li {
  border-block-start: 1px solid var(--hair);
  padding-block: .95rem;
  font-size: var(--step--1);
}
.refs li:last-child { border-block-end: 1px solid var(--hair); }
.refs__src {
  display: block;
  font-family: var(--font-data);
  font-size: var(--step--2);
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--fail);
  margin-block-end: .3rem;
}
[dir="rtl"] .refs__src { letter-spacing: 0; text-transform: none; font-size: var(--step--1); }
.refs p { max-inline-size: none; }

.refs__link { margin-block-start: .55rem; }
.refs__link a {
  display: inline-flex;
  align-items: center;
  min-block-size: 44px;
  padding-inline: .8rem;
  border: 1px solid var(--rule);
  background: var(--panel);
  font-family: var(--font-data);
  font-size: var(--step--1);
  text-decoration: none;
  box-shadow: inset 0 -3px 0 var(--trace);
}
.refs__link a:hover { background: var(--trace); box-shadow: none; }

/* ── Caveat ─────────────────────────────────────────────────────────────── */

.caveat {
  border: 1px solid var(--fail);
  background-color: var(--panel-3);
  background-image: var(--hatch);
  padding: 1.2rem .95rem;
  margin-block: 2rem;
}
.caveat h2 { font-size: var(--step-2); margin-block-end: .7rem; }

/* ── Footer ─────────────────────────────────────────────────────────────── */

footer {
  border-block-start: 1px solid var(--rule);
  background: var(--panel-2);
  margin-block-start: 2.5rem;
  padding-block: 1.6rem;
}
footer p {
  max-inline-size: none;
  margin: 0;
  font-size: var(--step--1);
  color: var(--graphite);
  text-align: center;
  padding-inline: var(--pad);
}
footer a {
  color: var(--ink);
  display: inline-flex;
  align-items: center;
  min-block-size: 44px;
  padding-inline: .15rem;
}

/* ── 640 ────────────────────────────────────────────────────────────────── */

@media (min-width: 40em) {
  :root { --pad: 1.75rem; --step-4: 2.6rem; --step-3: 1.9rem; }

  .site-head .wrap { flex-wrap: nowrap; min-block-size: 64px; }
  .nav { flex-basis: auto; order: 2; margin-inline-start: auto; }
  .nav ul { border-block-start: 0; gap: 0 1.3rem; }
  .lang-switch { order: 3; margin-inline-start: .4rem; }

  .hero { padding-block: 3.25rem 2.25rem; }
  .readout { padding: 1.2rem 1.2rem 1.35rem; }
  .module { padding: 2.7rem 1.6rem 1.9rem; }
  .instr { padding: 1.25rem 1.25rem 1.35rem; }
  .interlock__plate { padding-inline: 1.4rem; }
  .interlock__body { padding: 1.5rem 1.4rem 1.7rem; }
  .caveat { padding: 1.6rem 1.5rem; }
  .code { padding: 1.1rem 1.2rem; }
  .btn { flex: 0 0 auto; }
  .steps > li { grid-template-columns: 2.6rem 1fr; }
}

/* ── 768 ────────────────────────────────────────────────────────────────── */

@media (min-width: 48em) {
  :root { --step-4: 3.1rem; }

  .row__top { flex-wrap: nowrap; }
  .instruments { display: grid; gap: 1.1rem; }
  .instr { margin-block-end: 0; }

  .rules { display: grid; grid-template-columns: 1fr 1fr; gap: 0 2rem; }
  .rules li { border-block-end: 1px solid var(--hair); }

  .interlock__ledger { display: grid; grid-template-columns: 1fr 1fr; gap: 0 2rem; }
}

/* ── 1024 ───────────────────────────────────────────────────────────────── */

@media (min-width: 64em) {
  :root { --pad: 2.25rem; --step-4: 3.5rem; }

  .hero { padding-block: 4rem 2.75rem; }
  .hero h1 { max-inline-size: 20ch; }
  .instruments { grid-template-columns: repeat(3, 1fr); }
  .instr { display: flex; flex-direction: column; }
  .instr__limit { margin-block-start: auto; }
  .module { padding: 3rem 2.2rem 2.4rem; }
  .interlock__body { padding: 2rem 2.2rem 2.2rem; }
  .interlock h2 { font-size: var(--step-3); }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
}