:root{
    --brand: #174787;
    --brand-deep: #0b3a7a;
    --brand-glow: #0c3d70;
    --gradient-brand: linear-gradient(135deg, #313f53 0%, #063b81 55%, #06294d 100%);
    --gradient-soft: linear-gradient(180deg, #ffffff 0%, #ffffff 100%);
    --bg: #f4f8ff;
    --card: #ffffff;
    --text: #1a2540;
    --muted: #5a6a85;
    --border: #e3ebf7;
    --chip-bg: #e3edfb;
    --shadow-card: 0 4px 20px -8px rgba(11, 58, 122, .18), 0 1px 3px rgba(11, 58, 122, .06);
    --shadow-elegant: 0 18px 40px -12px rgba(11, 58, 122, .45);
}

*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  font-family:'Cairo','Tajawal',system-ui,sans-serif;
  background:var(--gradient-soft);
  color:var(--text);
  line-height:1.8;
  -webkit-font-smoothing:antialiased;
}
a{color:inherit;text-decoration:none}

.container{max-width:1180px;margin:0 auto;padding:4% 24px}

/* ===== HERO ===== */
.hero{
  position:relative;
  background:var(--gradient-brand);
  color:#fff;
  overflow:hidden;
}
.hero-dots{
  position:absolute;inset:0;opacity:.18;
  background-image:
    radial-gradient(circle at 20% 30%, #fff 1px, transparent 1px),
    radial-gradient(circle at 80% 70%, #fff 1px, transparent 1px);
  background-size:40px 40px;
}
.hero-shine{
  height:4px;
  background:linear-gradient(90deg, transparent, rgba(255,255,255,.6), transparent);
}
.hero-top{
  display:flex;align-items:center;justify-content:space-between;gap:16px;
  margin-bottom:32px;flex-wrap:wrap;
}
.tlp{
  display:inline-flex;align-items:center;gap:8px;
  font-size:12px;font-weight:800;letter-spacing:1.5px;
  padding:6px 12px;border:1px solid rgba(255,255,255,.35);
  border-radius:8px;background:rgba(255,255,255,.1);backdrop-filter:blur(8px);
}
.tlp .dot{width:8px;height:8px;border-radius:50%;background:#fff}
.hero-sub{font-size:14px;opacity:.85}
.hero-main{
  display:flex;align-items:center;gap:32px;flex-wrap:wrap;justify-content:center;
}
.logo{width:140px;height:auto;filter:drop-shadow(0 10px 25px rgba(0,0,0,.35))}
.hero-text{flex:1;min-width:260px;text-align:right}
.hero-text h1{
  font-size:clamp(26px,3vw,46px);font-weight:900;line-height:1.25;margin:0 0 10px;
}
.lead{font-size:clamp(16px,2vw,20px);opacity:.92;margin:0 0 18px;font-weight:500}
.badges{display:flex;flex-wrap:wrap;gap:8px}
.badge{
  font-size:12px;font-weight:600;
  padding:5px 12px;border-radius:999px;
  background:rgba(255,255,255,.15);border:1px solid rgba(255,255,255,.3);
  backdrop-filter:blur(8px);
}

/* ===== CARDS ===== */
.card{
  background:var(--card);
  border:1px solid var(--border);
  border-radius:18px;
  box-shadow:var(--shadow-card);
}
.preface-wrap{padding:40px 24px 8px}
.preface{padding:28px}
.card-head{display:flex;align-items:center;gap:12px;margin-bottom:14px}
.card-head h2{margin:0;font-size:22px;font-weight:800;color:var(--brand-deep)}
.icon-box{
  width:42px;height:42px;border-radius:12px;
  display:flex;align-items:center;justify-content:center;
  color:#fff;background:var(--gradient-brand);flex-shrink:0;
}
.icon-box svg{width:20px;height:20px}
.preface p{margin:0;font-size:17px;line-height:2;color:var(--text)}

/* ===== LAYOUT ===== */
.layout{
  display:grid;grid-template-columns:260px 1fr;gap:32px;
  padding-bottom:80px;align-items:start;
}
@media (max-width:880px){
  .layout{grid-template-columns:1fr}
}

/* ===== SIDEBAR / TOC ===== */
.sidebar{position:sticky;top:20px}
@media (max-width:880px){.sidebar{position:static}}
.toc{padding:20px}
.toc h3{
  margin:0 0 14px;font-size:14px;color:var(--brand-deep);
  display:flex;align-items:center;gap:8px;font-weight:800;
}
.toc h3 svg{width:16px;height:16px}
.toc nav{display:flex;flex-direction:column;gap:6px}
.toc a{
  display:block;padding:10px 14px;border-radius:10px;
  font-size:14px;font-weight:600;color:var(--text);
  transition:all .2s ease;
}
.toc a:hover{background:var(--chip-bg)}
.toc a.active{background:var(--gradient-brand);color:#fff;box-shadow:var(--shadow-card)}
.toc a .num{opacity:.7;font-size:11px;margin-left:6px}

/* ===== CONTENT ===== */
.content{display:flex;flex-direction:column;gap:48px;min-width:0}
.section-head{display:flex;align-items:center;gap:16px;margin-bottom:24px;flex-wrap:wrap}
.section-num{
  padding:8px 16px;border-radius:12px;color:#fff;font-weight:800;font-size:14px;
  background:var(--gradient-brand);
}
.section-head h2{margin:0;font-size:clamp(22px,2.6vw,30px);font-weight:900;color:var(--brand-deep)}
.section-intro{font-size:17px;color:var(--muted);margin:0 0 24px;padding-inline-start:4px}

.subs{display:grid;gap:20px}
.sub{
  border-radius:18px;overflow:hidden;background:var(--card);
  border:1px solid var(--border);box-shadow:var(--shadow-card);
  transition:transform .25s ease, box-shadow .25s ease;
}
.sub:hover{transform:translateY(-2px);box-shadow:0 10px 30px -10px rgba(11,58,122,.25)}
.sub-head{
  display:flex;align-items:center;gap:12px;
  padding:16px 22px;background:#eef4fc;border-bottom:1px solid var(--border);
}
.sub-head h3{margin:0;font-size:17px;font-weight:800;color:var(--brand-deep)}
.sub-list{margin:0;padding:22px;list-style:none;display:flex;flex-direction:column;gap:16px}
.sub-list li{display:flex;gap:14px;align-items:flex-start}
.chip{
  flex-shrink:0;margin-top:4px;
  padding:4px 10px;border-radius:7px;
  background:var(--chip-bg);color:var(--brand-deep);
  font-size:12px;font-weight:800;font-variant-numeric:tabular-nums;
  white-space:nowrap;
}
.sub-list p{margin:0;font-size:15.5px;line-height:2;color:#2a3654}

/* ===== FOOTER ===== */
.footer{
  margin-top:20px;padding:36px 0;color:#fff;background:var(--gradient-brand);
}
.footer-inner{display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap}
.footer-brand{display:flex;align-items:center;gap:12px}
.footer-brand img{width:48px;height:auto}
.b1{font-weight:800}
.b2{font-size:13px;opacity:.8}
.footer-meta{font-size:13px;opacity:.85}

/* ===== TO-TOP ===== */
.to-top{
  position:fixed;bottom:24px;left:24px;
  width:48px;height:48px;border:0;border-radius:50%;
  background:var(--gradient-brand);color:#fff;cursor:pointer;
  display:none;align-items:center;justify-content:center;
  box-shadow:var(--shadow-elegant);transition:transform .2s ease;
  z-index:50;
}
.to-top svg{width:20px;height:20px}
.to-top:hover{transform:scale(1.1)}
.to-top.show{display:flex}

/* scroll offset for TOC anchors */
section[id]{scroll-margin-top:16px}