/* ==========================================================
   Stylesheet — structured how-to workspace
   Mobile-first · system fonts · no scripts
   ========================================================== */

:root{
  --primary:#3730a3;
  --primary-soft:#eef0fb;
  --secondary:#1e1b4b;
  --accent:#a3e635;
  --accent-ink:#1c2b06;
  --bg:#f5f6fa;
  --surface:#ffffff;
  --surface-alt:#eceef6;
  --text:#22252e;
  --muted:#5a6170;
  --border:#d9dce7;
  --row-alt:#f2f3f9;
  --success:#15803d;
  --danger:#b91c1c;
  --radius:6px;
  --shadow:0 1px 2px rgba(23,25,48,.05),0 4px 16px rgba(23,25,48,.06);
  --wrap:1080px;
}

/* ---------- Reset & base ---------- */
*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  margin:0;
  font-family:system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  font-size:1rem;
  line-height:1.7;
  color:var(--text);
  background:var(--bg);
}
img{max-width:100%;height:auto}
main{display:block}
article{max-width:860px;margin:0 auto;padding:0 20px 56px}

h1,h2,h3,h4,h5,h6{line-height:1.25;color:var(--secondary);font-weight:700;margin:2.2em 0 .7em}
h1{font-size:clamp(1.7rem,4.5vw + .6rem,2.5rem);letter-spacing:-.02em;margin-top:0}
h2{font-size:1.45rem;padding-left:14px;border-left:4px solid var(--accent);scroll-margin-top:110px}
h3{font-size:1.15rem}
h4{font-size:1rem}
p{margin:0 0 1.1em}
ul,ol{margin:0 0 1.3em;padding-left:1.4em}
li{margin-bottom:.45em}
li::marker{color:var(--primary);font-weight:700}
strong{color:var(--secondary)}
hr{border:0;border-top:1px solid var(--border);margin:2.5em 0}

a{color:var(--primary);text-decoration:underline;text-underline-offset:.15em;text-decoration-thickness:1px}
a:hover{color:var(--secondary);text-decoration-thickness:2px}
:focus-visible{outline:3px solid var(--primary);outline-offset:2px;border-radius:2px}

::selection{background:var(--accent);color:var(--accent-ink)}

blockquote{
  margin:1.6em 0;padding:16px 20px;
  background:var(--surface);border-left:4px solid var(--primary);
  border-radius:var(--radius);color:var(--muted);box-shadow:var(--shadow);
}
blockquote p:last-child{margin-bottom:0}

figure{margin:28px 0;padding:0}
figcaption{margin-top:10px;font-size:.85rem;color:var(--muted)}

code{background:var(--surface-alt);border-radius:4px;padding:.1em .35em;font-size:.92em}

nav{font-size:.95rem}

/* ---------- Layout helper ---------- */
.wrap{max-width:var(--wrap);margin:0 auto;padding:0 20px}

/* ---------- Header ---------- */
.site-header{
  position:sticky;top:0;z-index:60;
  background:var(--secondary);
  border-bottom:3px solid var(--accent);
}
.site-header .wrap{
  display:flex;flex-wrap:wrap;align-items:center;
  gap:8px 18px;padding:10px 20px;
}
.brand{
  display:inline-flex;align-items:center;gap:10px;
  color:#fff;font-weight:700;font-size:1.02rem;letter-spacing:.01em;
  text-decoration:none;
}
.brand:hover{color:#fff;text-decoration:none}
.brand img{height:44px;width:auto;object-fit:contain;display:block}
.site-header :focus-visible{outline-color:var(--accent)}

.primary{display:flex;flex-wrap:wrap;gap:2px 4px;width:100%;padding-bottom:6px}
.primary a{
  color:#c7d2fe;text-decoration:none;font-weight:600;font-size:.85rem;
  padding:6px 10px;border-radius:var(--radius);
}
.primary a:hover{background:rgba(255,255,255,.12);color:#fff}
.primary a.active,
.active{background:var(--accent);color:var(--accent-ink)}
.primary a.active:hover{background:var(--accent);color:var(--accent-ink)}

/* ---------- Hero ---------- */
.hero{
  background:
    repeating-linear-gradient(90deg,rgba(255,255,255,.045) 0 1px,transparent 1px 44px),
    repeating-linear-gradient(0deg,rgba(255,255,255,.045) 0 1px,transparent 1px 44px),
    linear-gradient(135deg,var(--secondary) 0%,var(--primary) 100%);
  color:#dfe3fb;
  border-radius:calc(var(--radius) * 2);
  padding:32px 22px;
  margin:24px 0 34px;
}
.hero h1{color:#fff;margin:0 0 12px}
.hero :focus-visible{outline-color:var(--accent)}
.hero a{color:#e3ecc9}

.byline{font-size:.9rem;color:var(--muted);margin:0 0 18px}
.hero .byline{color:#b9c0ea}
.hero .byline strong{color:#fff}

.intro{max-width:64ch}
.intro p{font-size:1.06rem;line-height:1.65;color:#e6e9fc;margin-bottom:.6em}

.cta-row{display:flex;flex-wrap:wrap;gap:10px;margin-top:22px}

/* ---------- Buttons ---------- */
.btn{
  display:inline-flex;align-items:center;justify-content:center;
  padding:11px 20px;border-radius:var(--radius);
  font-weight:700;font-size:.95rem;line-height:1.2;
  text-decoration:none;border:2px solid transparent;
  transition:background-color .15s ease,color .15s ease,border-color .15s ease;
}
.btn:hover{text-decoration:none}
.btn-primary{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.btn-primary:hover{background:#bef264;border-color:#bef264;color:var(--accent-ink)}
.btn-secondary{background:transparent;border-color:rgba(255,255,255,.55);color:#fff}
.btn-secondary:hover{background:rgba(255,255,255,.12);border-color:#fff;color:#fff}

/* ---------- Table of contents ---------- */
.toc{
  background:var(--surface);border:1px solid var(--border);
  border-radius:var(--radius);box-shadow:var(--shadow);
  padding:20px 20px 16px;margin:0 0 40px;
}
.toc-title{
  margin:0 0 10px;font-size:.78rem;font-weight:700;
  text-transform:uppercase;letter-spacing:.14em;color:var(--muted);
}
.toc ol{list-style:none;margin:0;padding:0;counter-reset:toc;display:grid;gap:2px}
.toc li{margin:0;counter-increment:toc}
.toc a{
  display:flex;align-items:baseline;gap:10px;
  padding:7px 8px;border-radius:var(--radius);
  color:var(--text);font-weight:500;font-size:.93rem;text-decoration:none;
}
.toc a::before{
  content:counter(toc,decimal-leading-zero);
  font-size:.78rem;font-weight:700;color:var(--primary);
  font-variant-numeric:tabular-nums;flex:none;
}
.toc a:hover{background:var(--primary-soft);color:var(--primary)}

/* ---------- Figures & images ---------- */
.img-wrap{
  margin:28px 0;padding:14px;
  background:var(--surface);border:1px solid var(--border);
  border-radius:var(--radius);box-shadow:var(--shadow);
}
.img-wrap img{display:block;width:100%;height:auto;border-radius:calc(var(--radius) - 2px)}
.img-caption{margin:10px 2px 0;font-size:.85rem;color:var(--muted)}

/* ---------- Tables ---------- */
table{width:100%;border-collapse:collapse;font-size:.93rem;line-height:1.5;margin:0 0 1.5em}
thead th{
  background:var(--primary);color:#fff;text-align:left;
  padding:12px 14px;font-weight:700;white-space:nowrap;
}
tbody td{padding:11px 14px;border-bottom:1px solid var(--border);vertical-align:top}
tbody tr:nth-child(even){background:var(--row-alt)}
tbody tr:last-child td{border-bottom:0}

.table-wrap{
  overflow-x:auto;-webkit-overflow-scrolling:touch;
  margin:28px 0;background:var(--surface);
  border:1px solid var(--border);border-radius:var(--radius);
  box-shadow:var(--shadow);
}
.table-wrap table{margin:0;min-width:560px}

/* ---------- Mid-article callout ---------- */
.mid-cta{
  margin:40px 0;padding:24px 22px;
  background:var(--primary-soft);
  border:1px solid var(--border);border-left:4px solid var(--primary);
  border-radius:var(--radius);
}
.mid-cta h3{margin:0 0 8px;color:var(--secondary)}
.mid-cta p{margin:0 0 16px;color:var(--muted);max-width:60ch}

/* ---------- FAQ ---------- */
.faq{display:grid;gap:10px;margin:20px 0 8px}

details{
  background:var(--surface);border:1px solid var(--border);
  border-radius:var(--radius);box-shadow:var(--shadow);
}
summary{
  font-weight:700;font-size:1.08rem;line-height:1.4;
  cursor:pointer;padding:14px 44px 14px 16px;
  position:relative;list-style:none;color:var(--secondary);
  border-radius:var(--radius);
}
summary::-webkit-details-marker{display:none}
summary::after{
  content:"+";position:absolute;right:14px;top:50%;
  transform:translateY(-50%);
  width:24px;height:24px;border-radius:50%;
  background:var(--surface-alt);color:var(--primary);
  font-size:1.05rem;font-weight:700;line-height:24px;text-align:center;
}
summary:hover{color:var(--primary)}
details[open] summary{border-bottom:1px solid var(--border);border-radius:var(--radius) var(--radius) 0 0}
details[open] summary::after{content:"\2212";background:var(--accent);color:var(--accent-ink)}
details p{margin:0;padding:13px 16px 15px;color:var(--text)}
details p + p{padding-top:0}

/* ---------- Author box ---------- */
.author-box{
  display:flex;gap:16px;align-items:flex-start;
  margin:46px 0 8px;padding:20px;
  background:var(--surface);border:1px solid var(--border);
  border-left:4px solid var(--primary);border-radius:var(--radius);
  box-shadow:var(--shadow);
}
.author-box img{width:64px;height:64px;flex:none;border-radius:50%;background:var(--surface-alt)}
.author-name{margin:0;font-weight:700;font-size:1.02rem;color:var(--secondary)}
.author-role{
  margin:2px 0 8px;font-size:.76rem;font-weight:700;
  text-transform:uppercase;letter-spacing:.1em;color:var(--primary);
}
.author-bio{margin:0;font-size:.92rem;color:var(--muted)}

/* ---------- Footer ---------- */
footer{background:var(--secondary);color:#c9cdea;margin-top:60px;border-top:4px solid var(--accent)}
footer .wrap{padding:40px 20px 28px}
footer h4{color:#fff;margin:0 0 12px;font-size:.95rem}
footer p{font-size:.88rem;line-height:1.65;margin:0 0 .8em}
footer ul{list-style:none;margin:0;padding:0;display:grid;gap:8px}
footer li{margin:0}
footer a{color:#c7d2fe;text-decoration:none;font-size:.9rem}
footer a:hover{color:#fff;text-decoration:underline}
footer :focus-visible{outline-color:var(--accent)}

.cols{display:grid;gap:28px}

.disclaimer{
  margin:30px 0 0;padding-top:18px;
  border-top:1px solid rgba(255,255,255,.16);
  font-size:.8rem;line-height:1.6;color:#a6adda;
}

/* ---------- 700px and up ---------- */
@media (min-width:700px){
  article{padding:0 28px 68px}
  h2{font-size:1.6rem}

  .site-header .wrap{flex-wrap:nowrap;padding:10px 20px}
  .primary{width:auto;margin-left:auto;padding-bottom:0;justify-content:flex-end}
  .primary a{font-size:.88rem}

  .hero{padding:44px 40px;margin-top:32px}
  .toc ol{grid-template-columns:1fr 1fr;column-gap:20px}
  .cols{grid-template-columns:1.6fr 1fr 1fr;gap:36px}
  .mid-cta{padding:28px 30px}
  .author-box img{width:80px;height:80px}
}

/* ---------- 960px and up ---------- */
@media (min-width:960px){
  body{font-size:1.0625rem}
  h2{font-size:1.7rem}
  summary{font-size:1.15rem}

  .hero{padding:56px 54px}
  .intro p{font-size:1.12rem}
  .primary a{font-size:.9rem;padding:7px 12px}
  .table-wrap table{min-width:0}
  .img-wrap{padding:18px}
}

/* ---------- Motion preferences ---------- */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .btn{transition:none}
}