/* ==========================================================================
   The Natural Parallel Test — shared stylesheet
   Direction: annotated specimen sheet. Unbleached card stock, cold ink,
   aniline-violet determination stamp, prussian blue reserved for what passes.
   Mobile-first: base styles target ~360px; complexity added at 640/768/1024.
   All spacing uses logical properties so RTL flips correctly.
   ========================================================================== */

:root {
  --sheet:    #dedcd4;
  --sheet-2:  #d5d3c9;
  --slip:     #efeee9;
  --ink:      #16181a;
  --graphite: #55585b;
  --rule:     #b5b2a8;
  --stamp:    #5b3a8e;
  --confirm:  #1b4b76;

  --font-display: "Spectral", Georgia, "Times New Roman", serif;
  --font-body:    "Spectral", Georgia, "Times New Roman", serif;
  --font-ui:      "Archivo", "Helvetica Neue", Arial, sans-serif;
  --font-mono:    "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, monospace;

  --step--2: 0.6875rem;
  --step--1: 0.8125rem;
  --step-0:  1.0625rem;
  --step-1:  1.1875rem;
  --step-2:  1.375rem;
  --step-3:  1.75rem;
  --step-4:  2.25rem;

  --gap:      1.25rem;
  --band-pad: 2.75rem;
  --measure:  38rem;
}

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

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

body {
  margin: 0;
  background: var(--sheet);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--step-0);
  font-weight: 400;
  line-height: 1.62;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* Faint ruling, like the grain of card stock. Disabled in print-ish contexts. */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background: repeating-linear-gradient(
    to bottom,
    rgba(22, 24, 26, 0.028) 0 1px,
    transparent 1px 6px
  );
  z-index: 0;
}

body > * { position: relative; z-index: 1; }

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

a { color: var(--confirm); text-decoration-thickness: 1px; text-underline-offset: 0.18em; }
a:hover { color: var(--stamp); }
a:focus-visible,
button:focus-visible { outline: 2px solid var(--stamp); outline-offset: 3px; }

h1, h2, h3 { font-family: var(--font-display); font-weight: 300; margin: 0; line-height: 1.12; }
h1 { font-size: var(--step-4); letter-spacing: -0.015em; }
h2 { font-size: var(--step-3); letter-spacing: -0.01em; }
h3 { font-size: var(--step-1); font-weight: 600; line-height: 1.3; }
p  { margin: 0 0 1em; max-width: var(--measure); }
em { font-style: italic; }

.wrap {
  inline-size: 100%;
  max-inline-size: 74rem;
  margin-inline: auto;
  padding-inline: 1.25rem;
}

.skip {
  position: absolute;
  inset-inline-start: -9999px;
  top: 0;
  background: var(--ink);
  color: var(--slip);
  padding: 0.75rem 1rem;
  font-family: var(--font-ui);
  z-index: 20;
}
.skip:focus { inset-inline-start: 0; }

/* --- eyebrows and labels ------------------------------------------------ */

.eyebrow {
  font-family: var(--font-ui);
  font-size: var(--step--2);
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--stamp);
  margin: 0 0 0.85rem;
}

.note {
  font-size: var(--step--1);
  color: var(--graphite);
  line-height: 1.55;
}

.mono {
  font-family: var(--font-mono);
  font-size: 0.9em;
  font-variant-numeric: tabular-nums;
}

/* --- header ------------------------------------------------------------- */

.site-head {
  border-block-end: 1px solid var(--rule);
  background: var(--sheet);
}

.site-head .wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 1rem;
  padding-block: 0.75rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  min-block-size: 44px;
  color: var(--ink);
  text-decoration: none;
  font-family: var(--font-ui);
  font-weight: 700;
  font-size: var(--step--1);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  margin-inline-end: auto;
}
.brand svg { flex: none; }
.brand:hover { color: var(--stamp); }

.lang-switch {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-block-size: 44px;
  min-inline-size: 44px;
  padding-inline: 0.9rem;
  border: 1px solid var(--rule);
  color: var(--ink);
  text-decoration: none;
  font-family: var(--font-ui);
  font-size: var(--step--1);
  font-weight: 600;
  background: var(--slip);
}
.lang-switch:hover { border-color: var(--stamp); color: var(--stamp); }

.nav {
  inline-size: 100%;
  order: 3;
  border-block-start: 1px solid var(--rule);
  padding-block-start: 0.35rem;
}
.nav ul {
  display: flex;
  flex-wrap: wrap;
  gap: 0 1.15rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav a {
  display: inline-flex;
  align-items: center;
  min-block-size: 44px;
  font-family: var(--font-ui);
  font-size: var(--step--1);
  font-weight: 500;
  color: var(--graphite);
  text-decoration: none;
}
.nav a:hover { color: var(--stamp); }

/* --- hero --------------------------------------------------------------- */

.hero { padding-block: 2.5rem 2.75rem; }

.hero h1 { margin-block-end: 1.1rem; }
.hero h1 em { font-style: italic; }

.lede {
  font-size: var(--step-1);
  line-height: 1.5;
  max-inline-size: 34rem;
}

.rule-quote {
  margin: 1.75rem 0;
  padding-inline-start: 1.1rem;
  border-inline-start: 3px solid var(--stamp);
  font-family: var(--font-display);
  font-size: var(--step-2);
  font-weight: 300;
  line-height: 1.34;
  max-inline-size: 34rem;
}
.rule-quote p { margin: 0; max-inline-size: none; }
.rule-quote strong { font-weight: 600; }
.rule-quote cite {
  display: block;
  margin-block-start: 0.85rem;
  font-family: var(--font-ui);
  font-size: var(--step--2);
  font-style: normal;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--graphite);
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-block-start: 1.75rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-block-size: 44px;
  padding: 0.6rem 1.2rem;
  font-family: var(--font-ui);
  font-size: var(--step--1);
  font-weight: 600;
  letter-spacing: 0.04em;
  text-decoration: none;
  border: 1px solid var(--ink);
}
.btn--solid { background: var(--ink); color: var(--slip); }
.btn--solid:hover { background: var(--stamp); border-color: var(--stamp); color: var(--slip); }
.btn--ghost { background: transparent; color: var(--ink); }
.btn--ghost:hover { border-color: var(--stamp); color: var(--stamp); }

/* --- bands -------------------------------------------------------------- */

.band {
  border-block-start: 1px solid var(--rule);
  padding-block: var(--band-pad);
}

.band__code {
  font-family: var(--font-ui);
  font-size: var(--step--2);
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--stamp);
  margin: 0 0 0.9rem;
}

.band__body > h2 { margin-block-end: 0.9rem; }
.band__body > h2 + p { margin-block-start: 0; }

/* --- determination slips (the signature element) ------------------------ */

.slips {
  list-style: none;
  margin: 1.5rem 0 0;
  padding: 0;
  display: grid;
  gap: 1rem;
}

.slip {
  background: var(--slip);
  border: 1px solid var(--rule);
  padding: 1.1rem 1.15rem 1.25rem;
}

.slip__det {
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--graphite);
  margin: 0 0 0.7rem;
  padding-block-end: 0.6rem;
  border-block-end: 1px dotted var(--rule);
}

.slip__name {
  font-family: var(--font-display);
  font-size: var(--step-2);
  font-weight: 300;
  font-style: italic;
  line-height: 1.2;
  margin: 0 0 0.9rem;
  color: var(--ink);
}

.slip__mark {
  display: inline-block;
  margin: 0 0 0.8rem;
  padding: 0.28rem 0.7rem;
  border: 2px solid var(--stamp);
  color: var(--stamp);
  font-family: var(--font-ui);
  font-size: var(--step--2);
  font-weight: 700;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  transform: rotate(-3deg);
}
.slip__mark--contested { border-style: dashed; }

.slip__why { margin: 0; font-size: var(--step--1); line-height: 1.55; color: var(--ink); }

/* --- steps -------------------------------------------------------------- */

.steps {
  list-style: none;
  counter-reset: none;
  margin: 1.4rem 0 0;
  padding: 0;
  display: grid;
  gap: 0;
}
.steps li {
  display: grid;
  grid-template-columns: 2.4rem minmax(0, 1fr);
  align-items: baseline;
  gap: 0.75rem;
  padding-block: 0.6rem;
  border-block-end: 1px solid var(--rule);
}
.steps li:last-child { border-block-end: 0; }
.num {
  font-family: var(--font-mono);
  font-size: var(--step--1);
  font-weight: 600;
  color: var(--stamp);
  font-variant-numeric: tabular-nums;
}

/* --- ten mechanisms ----------------------------------------------------- */

.mechs {
  list-style: none;
  margin: 1.4rem 0 0;
  padding: 0;
  display: grid;
  gap: 1px;
  background: var(--rule);
  border: 1px solid var(--rule);
}
.mechs li {
  background: var(--sheet);
  padding: 0.95rem 1rem 1.05rem;
  display: grid;
  grid-template-columns: 2rem minmax(0, 1fr);
  gap: 0.15rem 0.6rem;
}
.mechs .num { grid-row: span 2; }
.mechs h3 { align-self: baseline; }
.mechs p { margin: 0; font-size: var(--step--1); color: var(--graphite); max-inline-size: none; }

/* --- seven levels ------------------------------------------------------- */

.ladder { list-style: none; margin: 1.4rem 0 0; padding: 0; }
.ladder li {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 0.15rem 1rem;
  padding-block: 0.85rem;
  border-block-end: 1px solid var(--rule);
}
.ladder li:first-child { border-block-start: 1px solid var(--rule); }
.lvl-name { font-family: var(--font-display); font-weight: 600; font-size: var(--step-1); }
.lvl-scale {
  font-family: var(--font-mono);
  font-size: var(--step--1);
  color: var(--graphite);
  text-align: end;
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}
.lvl-note { grid-column: 1 / -1; font-size: var(--step--1); color: var(--graphite); margin: 0; max-inline-size: none; }

/* --- four validity tests ------------------------------------------------ */

.tests { list-style: none; margin: 1.4rem 0 0; padding: 0; display: grid; gap: 1rem; }
.tests li {
  border-inline-start: 3px solid var(--rule);
  padding-inline-start: 1rem;
}
.tests h3 { display: flex; gap: 0.6rem; align-items: baseline; margin-block-end: 0.3rem; }
.tests p { margin: 0; font-size: var(--step--1); color: var(--graphite); }
.tests .fails {
  display: block;
  margin-block-start: 0.4rem;
  font-family: var(--font-mono);
  font-size: var(--step--2);
  color: var(--stamp);
}

/* --- twelve principles -------------------------------------------------- */

.principles {
  list-style: none;
  margin: 1.4rem 0 0;
  padding: 0;
  display: grid;
  gap: 0;
}
.principles li {
  display: grid;
  grid-template-columns: 2.2rem minmax(0, 1fr);
  gap: 0.1rem 0.6rem;
  padding-block: 0.7rem;
  border-block-end: 1px solid var(--rule);
}
.principles li:first-child { border-block-start: 1px solid var(--rule); }
.principles .num { grid-row: span 2; }
.principles .p-name { font-weight: 600; font-family: var(--font-display); }
.principles .p-test { margin: 0; font-size: var(--step--1); color: var(--graphite); max-inline-size: none; }

.callout {
  margin-block-start: 1.5rem;
  padding: 1rem 1.15rem;
  background: var(--slip);
  border-inline-start: 3px solid var(--stamp);
}
.callout p { margin: 0 0 0.6em; }
.callout p:last-child { margin: 0; }
.callout strong { font-weight: 600; }

/* --- classifications and overrides -------------------------------------- */

.classes { list-style: none; margin: 1.4rem 0 0; padding: 0; display: grid; gap: 0; }
.classes li {
  padding-block: 0.9rem;
  border-block-end: 1px solid var(--rule);
}
.classes li:first-child { border-block-start: 1px solid var(--rule); }
.classes h3 { margin-block-end: 0.25rem; }
.classes .band-score {
  font-family: var(--font-mono);
  font-size: var(--step--1);
  color: var(--confirm);
  display: block;
  margin-block-end: 0.3rem;
}
.classes p { margin: 0; font-size: var(--step--1); color: var(--graphite); }

.overrides {
  list-style: none;
  margin: 1.2rem 0 0;
  padding: 1.1rem 1.15rem;
  background: var(--slip);
  border: 1px solid var(--stamp);
}
.overrides li { padding-block: 0.55rem; border-block-end: 1px dotted var(--rule); }
.overrides li:last-child { border-block-end: 0; padding-block-end: 0; }
.overrides li:first-child { padding-block-start: 0; }
.overrides dfn {
  display: block;
  font-style: normal;
  font-weight: 600;
  font-family: var(--font-ui);
  font-size: var(--step--1);
  letter-spacing: 0.04em;
  color: var(--stamp);
  text-transform: uppercase;
}
.overrides span { font-size: var(--step--1); color: var(--ink); }

/* --- commands ----------------------------------------------------------- */

.cmds { list-style: none; margin: 1.4rem 0 0; padding: 0; }
.cmds li {
  padding-block: 0.85rem;
  border-block-end: 1px solid var(--rule);
}
.cmds li:first-child { border-block-start: 1px solid var(--rule); }
.cmds code {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--step-0);
  font-weight: 600;
  color: var(--ink);
  background: var(--slip);
  border: 1px solid var(--rule);
  padding: 0.2rem 0.5rem;
  margin-block-end: 0.4rem;
  direction: ltr;
  unicode-bidi: isolate;
}
.cmds p { margin: 0; font-size: var(--step--1); color: var(--graphite); max-inline-size: none; }

/* --- code blocks -------------------------------------------------------- */

pre {
  margin: 1.2rem 0;
  padding: 1rem 1.1rem;
  background: var(--ink);
  color: #e6e4dc;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: var(--step--1);
  line-height: 1.8;
  direction: ltr;
  text-align: start;
  unicode-bidi: isolate;
  border: 1px solid var(--ink);
}
pre code { font: inherit; color: inherit; }
pre .c { color: #a99cc4; }

p code, li code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--slip);
  padding: 0.1em 0.35em;
  border: 1px solid var(--rule);
  white-space: nowrap;
  direction: ltr;
  unicode-bidi: isolate;
}

/* --- limits ------------------------------------------------------------- */

.limits .band__body > p { font-size: var(--step-1); line-height: 1.55; }
.limits strong { font-weight: 600; }

/* --- footer ------------------------------------------------------------- */

footer {
  border-block-start: 1px solid var(--rule);
  margin-block-start: 0;
  padding-block: 2rem 2.5rem;
  padding-inline: 1.25rem;
  max-inline-size: 74rem;
  margin-inline: auto;
}
footer p {
  margin: 0;
  max-inline-size: none;
  font-family: var(--font-ui);
  font-size: var(--step--1);
  color: var(--graphite);
  line-height: 2;
}
footer a {
  display: inline-flex;
  align-items: center;
  min-block-size: 44px;
  color: var(--graphite);
}
footer a:hover { color: var(--stamp); }

/* ==========================================================================
   Breakpoints — additive only, never max-width for layout
   ========================================================================== */

@media (min-width: 640px) {
  :root {
    --step-4: 2.9rem;
    --step-3: 2rem;
    --band-pad: 3.25rem;
  }
  .wrap { padding-inline: 2rem; }
  footer { padding-inline: 2rem; }
  .slips { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .slips li:first-child { grid-column: 1 / -1; }
  .mechs { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .principles { grid-template-columns: repeat(2, minmax(0, 1fr)); column-gap: 2.5rem; }
  .principles li:nth-child(2) { border-block-start: 1px solid var(--rule); }
}

@media (min-width: 768px) {
  :root {
    --step-0: 1.125rem;
    --step-4: 3.5rem;
    --band-pad: 4rem;
  }
  .site-head .wrap { padding-block: 0.5rem; }
  .nav { inline-size: auto; order: 0; border-block-start: 0; padding-block-start: 0; }
  .nav ul { gap: 0 1.4rem; }
  .band {
    display: grid;
    grid-template-columns: 7rem minmax(0, 1fr);
    column-gap: 2.5rem;
  }
  .band__code { margin: 0.35rem 0 0; }
  .hero {
    padding-block: 4rem 3.5rem;
    display: grid;
    grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr);
    column-gap: 3.5rem;
    align-items: start;
  }
  .hero > .eyebrow,
  .hero > h1 { grid-column: 1 / -1; }
  .hero .lede { grid-column: 1; grid-row: 3; }
  .hero .rule-quote { grid-column: 2; grid-row: 3 / span 2; margin-block: 0.4rem 0; }
  .hero .actions { grid-column: 1; grid-row: 4; }
  .tests { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1.5rem 2.5rem; }
  .slips { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .slips li:first-child { grid-column: auto; }
}

@media (min-width: 1024px) {
  :root {
    --step-4: 4.25rem;
    --step-3: 2.25rem;
    --step-2: 1.5rem;
    --step-1: 1.25rem;
  }
  .wrap { padding-inline: 3rem; }
  footer { padding-inline: 3rem; }
  .band { grid-template-columns: 9rem minmax(0, 1fr); column-gap: 3.5rem; }
  .hero .lede { font-size: 1.375rem; }
  .ladder li { grid-template-columns: 14rem minmax(0, 1fr) auto; align-items: baseline; }
  .ladder .lvl-note { grid-column: 2 / 3; }
}

/* ==========================================================================
   RTL — Persian edition
   ========================================================================== */

[dir="rtl"] {
  --font-display: "Vazirmatn", "Segoe UI", Tahoma, sans-serif;
  --font-body:    "Vazirmatn", "Segoe UI", Tahoma, sans-serif;
  --font-ui:      "Vazirmatn", "Segoe UI", Tahoma, sans-serif;
  --measure: 40rem;
  line-height: 1.85;
}

[dir="rtl"] body { line-height: 1.85; }
[dir="rtl"] h1, [dir="rtl"] h2 { font-weight: 400; line-height: 1.35; letter-spacing: 0; }
[dir="rtl"] h3 { line-height: 1.6; }
[dir="rtl"] .eyebrow,
[dir="rtl"] .band__code,
[dir="rtl"] .slip__det,
[dir="rtl"] .slip__mark,
[dir="rtl"] .overrides dfn,
[dir="rtl"] .btn,
[dir="rtl"] .brand {
  letter-spacing: 0;
  text-transform: none;
}
[dir="rtl"] .slip__name { font-style: normal; font-weight: 500; line-height: 1.5; }
[dir="rtl"] .slip__mark { transform: rotate(3deg); }
[dir="rtl"] .rule-quote { font-weight: 400; line-height: 1.75; }
[dir="rtl"] .lede { line-height: 1.8; }
[dir="rtl"] .num { font-family: var(--font-body); font-weight: 700; }
[dir="rtl"] .lvl-scale { font-family: var(--font-body); unicode-bidi: isolate; }
[dir="rtl"] .classes .band-score { font-family: var(--font-body); }
[dir="rtl"] .slip__det { font-family: var(--font-body); }
[dir="rtl"] .tests .fails { font-family: var(--font-body); }
[dir="rtl"] .brand { font-size: var(--step-0); }

@media (min-width: 640px) {
  [dir="rtl"] { --step-3: 1.75rem; --step-4: 2.4rem; }
}
@media (min-width: 1024px) {
  [dir="rtl"] { --step-4: 3.25rem; --step-3: 2rem; }
}

/* ========================================================================== */

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