/* Road Design Exam Guide — "drafting sheet" look: paper, ink, road-sign yellow */
:root {
  --paper: #f6f4ee;
  --paper-2: #ece9e0;
  --card: #fffdf8;
  --ink: #1c2026;
  --ink-2: #454b55;
  --muted: #7b818b;
  --line: #d8d3c6;
  --grid: rgba(35, 100, 170, 0.07);
  --asphalt: #33373e;
  --asphalt-2: #4a4f57;
  --sign: #f2b705;
  --sign-soft: #fdf3cf;
  --sign-ink: #4a3600;
  --green: #1f7a4d;
  --green-soft: #e1f1e8;
  --blue: #2364aa;
  --blue-soft: #e3edf8;
  --red: #c23b2b;
  --red-soft: #fbe5e1;
  --water: #3d8fd6;
  --soil: #9a7246;
  --soil-2: #c8a678;
  --soil-3: #e2cda8;
  --grass: #6a9f4b;
  --rock: #8d8a85;
  --concrete: #b9b7b1;
  --shadow: 0 1px 0 rgba(0,0,0,.04), 0 8px 24px -12px rgba(30, 25, 10, .18);
  --radius: 10px;
  --font: "Barlow", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-cond: "Barlow Condensed", "Barlow", system-ui, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, monospace;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #14171b; --paper-2: #1b1f25; --card: #1d2228;
    --ink: #ecebe6; --ink-2: #c3c6cc; --muted: #8e939c; --line: #313740;
    --grid: rgba(120, 170, 230, 0.06);
    --asphalt: #4a4f58; --asphalt-2: #5d636d;
    --sign-soft: #3a2f0e; --sign-ink: #ffe28a;
    --green: #4cc28a; --green-soft: #15302a;
    --blue: #6aa6e8; --blue-soft: #172a40;
    --red: #ff7b68; --red-soft: #3b1e1a;
    --soil: #b08a5e; --soil-2: #8c6c47; --soil-3: #6f5638;
    --concrete: #7d7b77;
    --shadow: 0 1px 0 rgba(255,255,255,.03), 0 10px 28px -14px rgba(0,0,0,.7);
  }
}
:root[data-theme="dark"] {
  --paper: #14171b; --paper-2: #1b1f25; --card: #1d2228;
  --ink: #ecebe6; --ink-2: #c3c6cc; --muted: #8e939c; --line: #313740;
  --grid: rgba(120, 170, 230, 0.06);
  --asphalt: #4a4f58; --asphalt-2: #5d636d;
  --sign-soft: #3a2f0e; --sign-ink: #ffe28a;
  --green: #4cc28a; --green-soft: #15302a;
  --blue: #6aa6e8; --blue-soft: #172a40;
  --red: #ff7b68; --red-soft: #3b1e1a;
  --soil: #b08a5e; --soil-2: #8c6c47; --soil-3: #6f5638;
  --concrete: #7d7b77;
  --shadow: 0 1px 0 rgba(255,255,255,.03), 0 10px 28px -14px rgba(0,0,0,.7);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 16px; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.6;
  color: var(--ink);
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 24px 24px;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--blue); }
b, strong { font-weight: 600; }
code, .mono { font-family: var(--mono); font-size: .88em; }
code { background: var(--paper-2); padding: .1em .35em; border-radius: 4px; }

/* ---------- layout ---------- */
.shell { display: grid; grid-template-columns: 280px minmax(0, 1fr); min-height: 100vh; }
.side {
  position: sticky; top: 0; height: 100vh; overflow-y: auto;
  background: var(--asphalt); color: #e9e7e1;
  padding: 22px 18px 40px;
  border-right: 4px solid var(--sign);
}
.side .brand { display: flex; gap: 10px; align-items: center; margin-bottom: 18px; }
.side .brand svg { flex: none; }
.side .brand b { font-family: var(--font-cond); font-size: 1.25rem; letter-spacing: .02em; line-height: 1.1; display: block; }
.side .brand span { font-size: .78rem; color: #b9bcc2; }
.side .group { font-family: var(--font-cond); text-transform: uppercase; letter-spacing: .12em; font-size: .74rem; color: var(--sign); margin: 18px 0 6px; }
.side nav a {
  display: flex; gap: 10px; align-items: baseline;
  color: #dcdad3; text-decoration: none; font-size: .93rem;
  padding: 5px 8px; border-radius: 6px; line-height: 1.3;
}
.side nav a .n { font-family: var(--mono); font-size: .72rem; color: #9ba0a8; width: 20px; flex: none; }
.side nav a:hover { background: rgba(255,255,255,.07); }
.side nav a.active { background: rgba(242,183,5,.16); color: #fff; }
.side nav a.active .n { color: var(--sign); }
.side nav a.done .n::after { content: " ✓"; color: #7fd6a4; }
.side .meter { margin-top: 20px; font-size: .8rem; color: #b9bcc2; }
.side .meter .bar { height: 6px; background: rgba(255,255,255,.12); border-radius: 3px; margin-top: 6px; overflow: hidden; }
.side .meter .bar i { display: block; height: 100%; width: 0; background: var(--sign); transition: width .4s; }
.theme-btn {
  margin-top: 16px; background: transparent; color: #dcdad3; border: 1px solid rgba(255,255,255,.2);
  border-radius: 6px; padding: 6px 10px; font: inherit; font-size: .82rem; cursor: pointer;
}

main { padding: 36px clamp(16px, 4vw, 56px) 120px; max-width: 980px; min-width: 0; }

.topbar { display: none; }

@media (max-width: 920px) {
  .shell { grid-template-columns: minmax(0, 1fr); }
  .side {
    position: fixed; inset: 0 auto 0 0; width: min(300px, 86vw); z-index: 50;
    transform: translateX(-105%); transition: transform .25s ease;
  }
  .side.open { transform: none; box-shadow: 0 0 0 100vmax rgba(0,0,0,.45); }
  .topbar {
    display: flex; align-items: center; gap: 12px; position: sticky; top: 0; z-index: 40;
    background: var(--asphalt); color: #fff; padding: 10px 16px; border-bottom: 3px solid var(--sign);
  }
  .topbar button { background: var(--sign); color: #222; border: 0; border-radius: 6px; padding: 6px 10px; font: 600 .9rem var(--font); }
  .topbar b { font-family: var(--font-cond); font-size: 1.05rem; letter-spacing: .02em; }
  main { padding-top: 22px; }
  html { scroll-padding-top: 64px; }
}

/* ---------- hero ---------- */
.hero { margin-bottom: 40px; }
.hero .kicker {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: var(--font-cond); text-transform: uppercase; letter-spacing: .14em; font-size: .8rem;
  background: var(--sign); color: #2a2000; padding: 3px 10px; border-radius: 3px; font-weight: 600;
}
.hero h1 {
  font-family: var(--font-cond); font-weight: 700; font-size: clamp(2.2rem, 5.4vw, 3.6rem);
  line-height: 1.02; margin: 14px 0 12px; letter-spacing: -.005em;
}
.hero h1 em { font-style: normal; color: var(--blue); }
.hero p.lead { font-size: 1.1rem; color: var(--ink-2); max-width: 64ch; margin: 0 0 18px; }
.road-strip { height: 46px; margin: 18px 0 8px; position: relative; overflow: hidden; border-radius: 6px; background: var(--asphalt); }
.road-strip::before {
  content: ""; position: absolute; left: 0; right: 0; top: 50%; height: 4px; margin-top: -2px;
  background: repeating-linear-gradient(90deg, var(--sign) 0 28px, transparent 28px 52px);
  animation: dash 1.4s linear infinite;
}
@keyframes dash { to { background-position: -52px 0; } }
@media (prefers-reduced-motion: reduce) { .road-strip::before { animation: none; } }

.howto { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 12px; margin: 18px 0 0; }
.howto > div { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 12px 14px; font-size: .93rem; color: var(--ink-2); }
.howto b { display: block; color: var(--ink); font-family: var(--font-cond); font-size: 1.05rem; letter-spacing: .01em; }

/* ---------- lessons ---------- */
.lesson { padding-top: 26px; margin-top: 30px; border-top: 2px solid var(--ink); }
.part-head { margin: 64px 0 0; font-family: var(--font-cond); text-transform: uppercase; letter-spacing: .14em; color: var(--muted); font-size: .9rem; }
.part-head + .lesson { margin-top: 8px; }
.lesson-head { display: flex; gap: 16px; align-items: flex-start; }
.lesson-head .num {
  font-family: var(--font-cond); font-weight: 700; font-size: 2.6rem; line-height: .9;
  color: var(--sign); -webkit-text-stroke: 1.2px var(--ink); flex: none; min-width: 56px;
}
.lesson h2 { font-family: var(--font-cond); font-weight: 700; font-size: clamp(1.6rem, 3.4vw, 2.15rem); line-height: 1.08; margin: 0 0 6px; }
.src { font-size: .8rem; color: var(--muted); font-family: var(--mono); }
.lesson h3 { font-family: var(--font-cond); font-size: 1.3rem; margin: 26px 0 6px; letter-spacing: .01em; }
.lesson p { margin: 10px 0; }
.lesson ul, .lesson ol { padding-left: 1.3em; margin: 8px 0 12px; }
.lesson li { margin: 4px 0; }
.lesson li::marker { color: var(--muted); }
.tldr {
  margin: 16px 0; padding: 12px 16px; border-radius: var(--radius);
  background: var(--card); border: 1px solid var(--line); box-shadow: var(--shadow);
}
.tldr::before { content: "In one line"; display: block; font-family: var(--font-cond); text-transform: uppercase; letter-spacing: .12em; font-size: .74rem; color: var(--muted); }

.callout { margin: 16px 0; padding: 12px 16px 12px 46px; border-radius: 8px; position: relative; font-size: .97rem; }
.callout::before { position: absolute; left: 14px; top: 11px; font-size: 1.1rem; line-height: 1.4; }
.callout.star { background: var(--sign-soft); color: var(--sign-ink); border-left: 4px solid var(--sign); }
.callout.star::before { content: "★"; color: #c99700; }
.callout.star b:first-child { text-transform: uppercase; letter-spacing: .08em; font-size: .78rem; font-family: var(--font-cond); display: block; }
.callout.why { background: var(--blue-soft); border-left: 4px solid var(--blue); }
.callout.why::before { content: "?"; font-weight: 700; color: var(--blue); font-family: var(--font-cond); font-size: 1.3rem; }
.callout.warn { background: var(--red-soft); border-left: 4px solid var(--red); }
.callout.warn::before { content: "!"; font-weight: 700; color: var(--red); font-family: var(--font-cond); font-size: 1.3rem; }
.callout.tip { background: var(--green-soft); border-left: 4px solid var(--green); }
.callout.tip::before { content: "✓"; color: var(--green); font-weight: 700; }

.nums { display: flex; flex-wrap: wrap; gap: 8px; margin: 14px 0; }
.nums span {
  display: inline-flex; align-items: baseline; gap: 8px;
  background: var(--card); border: 1px solid var(--line); border-radius: 999px;
  padding: 4px 12px 4px 4px; font-size: .9rem; color: var(--ink-2);
}
.nums span b { font-family: var(--mono); font-weight: 600; background: var(--ink); color: var(--paper); border-radius: 999px; padding: 1px 9px; font-size: .84rem; }

table.t { width: 100%; border-collapse: collapse; margin: 12px 0 16px; font-size: .93rem; background: var(--card); border-radius: 8px; overflow: hidden; box-shadow: var(--shadow); }
.t th, .t td { padding: 8px 12px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
.t th { font-family: var(--font-cond); text-transform: uppercase; letter-spacing: .06em; font-size: .8rem; background: var(--paper-2); color: var(--ink-2); }
.t tr:last-child td { border-bottom: 0; }
.t td.mono, .t td .mono { font-family: var(--mono); font-size: .85rem; }
.table-wrap { overflow-x: auto; }

.twocol { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 14px 0; }
@media (max-width: 640px) { .twocol { grid-template-columns: 1fr; } }
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px 16px; box-shadow: var(--shadow); }
.card h4 { margin: 0 0 6px; font-family: var(--font-cond); font-size: 1.15rem; }
.card p, .card ul { margin: 6px 0; font-size: .95rem; }

/* ---------- figures ---------- */
.fig { margin: 20px 0 24px; background: var(--card); border: 1px solid var(--line); border-radius: 12px; box-shadow: var(--shadow); overflow: hidden; }
.fig-head { display: flex; justify-content: space-between; align-items: baseline; gap: 10px; padding: 10px 16px; border-bottom: 1px dashed var(--line); }
.fig-head b { font-family: var(--font-cond); font-size: 1.05rem; letter-spacing: .02em; }
.fig-head span { font-family: var(--mono); font-size: .72rem; color: var(--muted); text-transform: uppercase; letter-spacing: .08em; }
.fig svg { display: block; width: 100%; height: auto; }
.fig .stage { padding: 8px 10px 0; }
.controls { display: flex; flex-wrap: wrap; gap: 10px 18px; align-items: center; padding: 10px 16px 12px; }
.controls label { display: flex; flex-direction: column; gap: 2px; font-size: .82rem; color: var(--ink-2); font-weight: 600; min-width: 170px; flex: 1 1 200px; }
.controls label output { font-family: var(--mono); color: var(--ink); font-weight: 600; }
.controls input[type=range] { width: 100%; accent-color: var(--blue); }
.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 8px; overflow: hidden; flex-wrap: wrap; }
.seg button { background: transparent; border: 0; border-right: 1px solid var(--line); padding: 6px 12px; font: 600 .85rem var(--font); color: var(--ink-2); cursor: pointer; }
.seg button:last-child { border-right: 0; }
.seg button[aria-pressed="true"] { background: var(--ink); color: var(--paper); }
.btn { background: var(--ink); color: var(--paper); border: 0; border-radius: 8px; padding: 7px 14px; font: 600 .88rem var(--font); cursor: pointer; }
.btn.ghost { background: transparent; color: var(--ink); border: 1px solid var(--line); }
.btn:focus-visible, .seg button:focus-visible, .opt:focus-visible { outline: 3px solid var(--sign); outline-offset: 2px; }
.readout { display: flex; flex-wrap: wrap; gap: 6px 18px; padding: 10px 16px; background: var(--asphalt); color: #f1efe9; font-family: var(--mono); font-size: .82rem; }
.readout b { color: var(--sign); font-weight: 600; }
.readout .bad { color: #ff9a8a; }
.readout .ok { color: #8fe0b0; }
.caption { padding: 10px 16px 14px; font-size: .9rem; color: var(--ink-2); border-top: 1px dashed var(--line); }

/* svg text */
.fig svg text { font-family: var(--font); fill: var(--ink); }
.fig svg .lbl { font-size: 13px; font-weight: 600; }
.fig svg .sm { font-size: 11px; fill: var(--ink-2); }
.fig svg .mono { font-family: var(--mono); font-size: 11px; }
.hot { cursor: pointer; transition: opacity .2s; }
.hot:hover, .hot.on { filter: brightness(1.12); }
.tip-box { min-height: 3.2em; }

/* stepper */
.stepper { display: flex; gap: 6px; flex-wrap: wrap; padding: 12px 16px 0; }
.stepper button {
  border: 1px solid var(--line); background: var(--paper); color: var(--ink-2); border-radius: 999px;
  padding: 5px 12px; font: 600 .82rem var(--font); cursor: pointer;
}
.stepper button[aria-pressed="true"] { background: var(--sign); border-color: var(--sign); color: #2a2000; }
.step-body { padding: 12px 16px 16px; font-size: .95rem; }
.step-body h4 { margin: 0 0 4px; font-family: var(--font-cond); font-size: 1.2rem; }

/* workflow list */
ol.flow { list-style: none; padding: 0; counter-reset: f; margin: 14px 0; }
ol.flow li { counter-increment: f; position: relative; padding: 10px 12px 10px 52px; margin: 0; border-left: 2px dashed var(--line); margin-left: 18px; }
ol.flow li::before {
  content: counter(f); position: absolute; left: -17px; top: 8px; width: 32px; height: 32px; border-radius: 50%;
  background: var(--card); border: 2px solid var(--ink); display: grid; place-items: center;
  font-family: var(--mono); font-size: .85rem; font-weight: 600;
}
ol.flow li:last-child { border-left-color: transparent; }
ol.flow li b.cmd { font-family: var(--mono); font-weight: 600; font-size: .86rem; background: var(--paper-2); padding: 1px 6px; border-radius: 4px; }
.path { font-family: var(--mono); font-size: .86rem; background: var(--ink); color: var(--paper); padding: 2px 8px; border-radius: 4px; white-space: normal; }

/* cheat sheet */
.cheat { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 10px; margin: 14px 0; }
.cheat > div { background: var(--card); border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px; transition: border-color .15s, transform .15s; }
.cheat > div:hover { border-color: var(--sign); transform: translateY(-1px); }
.cheat .v { font-family: var(--font-cond); font-weight: 700; font-size: 1.55rem; line-height: 1.05; color: var(--ink); }
.cheat .k { font-size: .86rem; color: var(--ink-2); line-height: 1.35; margin-top: 2px; }
.cheat a { color: inherit; text-decoration: none; }

/* glossary */
dl.gloss { display: grid; grid-template-columns: minmax(150px, 220px) 1fr; gap: 0; margin: 14px 0; background: var(--card); border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
dl.gloss dt, dl.gloss dd { margin: 0; padding: 8px 12px; border-bottom: 1px solid var(--line); font-size: .93rem; }
dl.gloss dt { font-weight: 600; background: var(--paper-2); }
@media (max-width: 560px) { dl.gloss { grid-template-columns: 1fr; } dl.gloss dt { border-bottom: 0; padding-bottom: 2px; } }

/* ---------- quiz ---------- */
.quiz-bar { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; margin: 14px 0; }
.quiz-bar select { font: 600 .9rem var(--font); padding: 6px 10px; border-radius: 8px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }
.score { font-family: var(--mono); font-size: .9rem; color: var(--ink-2); margin-left: auto; }
.q { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 16px 18px; margin: 14px 0; box-shadow: var(--shadow); }
.q .qtag { font-family: var(--mono); font-size: .72rem; color: var(--muted); text-transform: uppercase; letter-spacing: .06em; }
.q .qtext { font-weight: 600; margin: 4px 0 10px; font-size: 1.02rem; }
.opt {
  display: block; width: 100%; text-align: left; background: var(--paper); color: var(--ink);
  border: 1.5px solid var(--line); border-radius: 8px; padding: 9px 12px; margin: 7px 0;
  font: 500 .96rem var(--font); cursor: pointer; transition: border-color .15s, background .15s;
}
.opt:hover:not([disabled]) { border-color: var(--ink-2); }
.opt[disabled] { cursor: default; }
.opt.right { border-color: var(--green); background: var(--green-soft); }
.opt.wrong { border-color: var(--red); background: var(--red-soft); }
.opt .k { font-family: var(--mono); font-weight: 600; margin-right: 8px; color: var(--muted); }
.explain { margin-top: 10px; padding: 10px 12px; border-radius: 8px; background: var(--paper-2); font-size: .93rem; display: none; }
.explain.show { display: block; animation: rise .25s ease; }
.explain a { font-weight: 600; }
@keyframes rise { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }
.result { text-align: center; padding: 22px; border-radius: 12px; background: var(--asphalt); color: #fff; margin: 18px 0; }
.result .big { font-family: var(--font-cond); font-size: 3rem; font-weight: 700; color: var(--sign); line-height: 1; }

footer { margin-top: 70px; padding-top: 16px; border-top: 1px solid var(--line); font-size: .85rem; color: var(--muted); }

/* animations used by SVG */
@keyframes flow { to { stroke-dashoffset: -40; } }
.flowing { stroke-dasharray: 6 8; animation: flow 1s linear infinite; }
@keyframes drip { 0% { opacity: 0; } 15% { opacity: 1; } 85% { opacity: 1; } 100% { opacity: 0; } }
@media (prefers-reduced-motion: reduce) { .flowing { animation: none; } }

/* svg paint helpers (presentation attributes can't use var()) */
.f-asph{fill:var(--asphalt)} .f-asph2{fill:var(--asphalt-2)} .f-soil{fill:var(--soil)} .f-soil2{fill:var(--soil-2)} .f-soil3{fill:var(--soil-3)}
.f-grass{fill:var(--grass)} .f-water{fill:var(--water)} .f-conc{fill:var(--concrete)} .f-rock{fill:var(--rock)} .f-sign{fill:var(--sign)}
.f-card{fill:var(--card)} .f-paper{fill:var(--paper-2)} .f-red{fill:var(--red)} .f-blue{fill:var(--blue)} .f-green{fill:var(--green)} .f-ink{fill:var(--ink)} .f-none{fill:none}
.f-redsoft{fill:var(--red-soft)} .f-bluesoft{fill:var(--blue-soft)} .f-signsoft{fill:var(--sign-soft)} .f-greensoft{fill:var(--green-soft)}
.s-ink{stroke:var(--ink)} .s-ink2{stroke:var(--ink-2)} .s-line{stroke:var(--line)} .s-muted{stroke:var(--muted)} .s-blue{stroke:var(--blue)} .s-red{stroke:var(--red)}
.s-green{stroke:var(--green)} .s-water{stroke:var(--water)} .s-sign{stroke:var(--sign)} .s-soil{stroke:var(--soil)} .s-asph{stroke:var(--asphalt)} .s-card{stroke:var(--card)}
.fig svg .t-muted{fill:var(--muted)} .fig svg .t-red{fill:var(--red)} .fig svg .t-blue{fill:var(--blue)} .fig svg .t-green{fill:var(--green)} .fig svg .t-white{fill:#fff} .fig svg .t-ink2{fill:var(--ink-2)} .fig svg .t-sign{fill:var(--sign)}
.fig svg .title { font-family: var(--font-cond); font-weight: 700; font-size: 15px; letter-spacing: .04em; text-transform: uppercase; fill: var(--ink-2); }
.chips { display: flex; flex-wrap: wrap; gap: 6px; padding: 10px 16px 0; }
.chips button { border: 1px solid var(--line); background: var(--paper); color: var(--ink); border-radius: 999px; padding: 4px 11px; font: 600 .82rem var(--font); cursor: pointer; }
.chips button[aria-pressed="true"] { background: var(--blue); border-color: var(--blue); color: #fff; }
.info { padding: 10px 16px 14px; font-size: .95rem; min-height: 4.4em; }
.info b { font-family: var(--font-cond); font-size: 1.08rem; letter-spacing: .01em; }
.night { transition: fill .4s; }
.fig svg .hot.on { stroke: #e0322b; stroke-width: 3px; }
.fig svg .hot { cursor: pointer; }

/* keep long formulas and paths from widening the page on phones */
code, .path, b.cmd, .readout span { overflow-wrap: anywhere; }
.fig-head { flex-wrap: wrap; }
@media (max-width: 520px) {
  .fig-head span { display: none; }
  .controls label { min-width: 0; flex-basis: 100%; }
  .lesson-head .num { font-size: 2rem; min-width: 40px; }
}

.quiz-bar select { max-width: 100%; min-width: 0; flex: 1 1 220px; }