/* ===== gstack Guide - "Gear Shift" Design System ===== */
/* YC Orange warmth + Terminal green code + Charcoal depth */

@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500&family=Space+Grotesk:wght@500;600;700&display=swap');

:root {
  --bg-deep: #121212;
  --bg-surface: #1a1a1a;
  --bg-elevated: #242424;
  --bg-code: #0d0d0d;

  --yc-orange: #ff6600;
  --yc-glow: rgba(255,102,0,0.10);
  --yc-border: rgba(255,102,0,0.20);
  --yc-hover: #ff8533;

  --terminal: #39ff14;
  --terminal-glow: rgba(57,255,20,0.08);
  --terminal-dim: #2ecc40;

  --gold: #fbbf24;
  --gold-glow: rgba(251,191,36,0.12);

  --text-bright: #f5f5f5;
  --text-body: #b0b0b0;
  --text-dim: #707070;
  --text-muted: #4a4a4a;

  --border: rgba(255,255,255,0.07);
  --border-orange: rgba(255,102,0,0.18);

  --sidebar-w: 270px;
  --header-h: 54px;

  --font-heading: 'Space Grotesk', sans-serif;
  --font-body: 'DM Sans', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  --ease: cubic-bezier(0.25,0.46,0.45,0.94);
  --transition: all 0.2s var(--ease);
}

*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;font-size:16px}
body{font-family:var(--font-body);background:var(--bg-deep);color:var(--text-bright);line-height:1.75;min-height:100vh;overflow-x:hidden}

/* ===== NOISE TEXTURE ===== */
body::after{
  content:'';position:fixed;inset:0;z-index:0;pointer-events:none;
  opacity:0.025;
  background-image:url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.65' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* ===== SIDEBAR ===== */
.sidebar{
  position:fixed;left:0;top:0;bottom:0;width:var(--sidebar-w);
  background:var(--bg-surface);border-right:1px solid var(--border);
  overflow-y:auto;z-index:100;padding:18px 0;
  transition:transform 0.35s var(--ease);
}
.sidebar-logo{padding:0 18px 14px;border-bottom:1px solid var(--border);margin-bottom:10px}
.sidebar-logo h2{
  font-family:var(--font-mono);font-size:1.1rem;font-weight:700;
  color:var(--yc-orange);letter-spacing:0.02em;
}
.sidebar-logo .sub{font-family:var(--font-mono);font-size:0.62rem;color:var(--text-dim);margin-top:3px}

.sidebar nav{padding:0 10px}
.sidebar nav a{
  display:block;padding:6px 12px;margin:1px 0;font-size:0.78rem;
  color:var(--text-body);text-decoration:none;border-radius:3px;
  transition:var(--transition);cursor:pointer;border-left:2px solid transparent;
}
.sidebar nav a:hover{background:var(--yc-glow);color:var(--text-bright)}
.sidebar nav a.active{background:var(--yc-glow);color:var(--yc-orange);border-left-color:var(--yc-orange);font-weight:500}
.sidebar nav a.chapter-link{font-family:var(--font-heading);font-weight:600;color:var(--text-bright);margin-top:10px;font-size:0.82rem}
.sidebar nav a.section-link{padding-left:24px;font-size:0.74rem}

/* ===== AUTHOR BAR ===== */
.author-bar{
  position:fixed;top:0;right:0;left:var(--sidebar-w);height:var(--header-h);
  background:rgba(18,18,18,0.85);backdrop-filter:blur(14px);-webkit-backdrop-filter:blur(14px);
  border-bottom:1px solid var(--border);display:flex;align-items:center;
  justify-content:flex-end;padding:0 24px;z-index:90;
}
.author-link{
  display:flex;align-items:center;gap:8px;text-decoration:none;
  padding:6px 14px;border-radius:3px;background:var(--gold-glow);
  border:1px solid rgba(251,191,36,0.22);transition:var(--transition);cursor:pointer;
}
.author-link:hover{background:rgba(251,191,36,0.18);transform:translateY(-1px)}
.author-link span{color:var(--gold);font-family:var(--font-heading);font-weight:600;font-size:0.8rem}

/* ===== MAIN ===== */
.main-content{position:relative;z-index:1;margin-left:var(--sidebar-w);padding:calc(var(--header-h) + 32px) 44px 80px;max-width:900px}

/* ===== HERO ===== */
.hero{text-align:center;padding:44px 0 40px;border-bottom:1px solid var(--border);margin-bottom:44px;position:relative}
.hero h1{
  font-family:var(--font-heading);font-size:2.8rem;font-weight:700;
  color:var(--yc-orange);line-height:1.15;margin-bottom:8px;
  text-shadow:0 0 30px rgba(255,102,0,0.2);
}
.hero .subtitle{font-family:var(--font-body);color:var(--text-body);font-size:1rem;font-weight:300;margin-bottom:4px}
.hero .meta{font-family:var(--font-mono);color:var(--text-dim);font-size:0.72rem;letter-spacing:0.04em}
.hero .meta strong{color:var(--text-body)}
.github-link{
  display:inline-flex;align-items:center;gap:6px;margin-top:10px;
  padding:5px 12px;font-family:var(--font-mono);font-size:0.72rem;
  color:var(--text-body);text-decoration:none;border:1px solid var(--border);
  background:var(--bg-code);transition:var(--transition);cursor:pointer;
}
.github-link:hover{border-color:var(--yc-border);color:var(--yc-orange)}
.github-link svg{flex-shrink:0}

.hero .stats{display:flex;justify-content:center;gap:14px;margin-top:24px;flex-wrap:wrap}
.hero .stat{
  text-align:center;padding:12px 20px;background:var(--bg-surface);
  border:1px solid var(--border);border-top:2px solid var(--yc-orange);
}
.hero .stat .num{font-family:var(--font-heading);font-size:1.6rem;font-weight:700;color:var(--yc-orange);line-height:1.2}
.hero .stat .label{font-family:var(--font-mono);font-size:0.62rem;color:var(--text-dim);margin-top:3px;letter-spacing:0.05em;text-transform:uppercase}

/* ===== CHAPTERS ===== */
.chapter{margin-bottom:52px;scroll-margin-top:calc(var(--header-h) + 18px);animation:fadeIn 0.35s ease-out forwards}
.chapter>h2{
  font-family:var(--font-heading);font-size:1.6rem;font-weight:700;color:var(--text-bright);
  padding-bottom:8px;border-bottom:2px solid var(--yc-orange);margin-bottom:22px;
  scroll-margin-top:calc(var(--header-h) + 18px);
}
.chapter h3{font-family:var(--font-heading);font-size:1.1rem;font-weight:600;color:var(--text-bright);margin:26px 0 10px;scroll-margin-top:calc(var(--header-h) + 18px)}
.chapter h4{font-family:var(--font-heading);font-size:0.95rem;font-weight:600;color:var(--yc-orange);margin:18px 0 8px}
.chapter p{margin-bottom:12px;color:var(--text-body);font-weight:400}
.chapter ul,.chapter ol{padding-left:20px;margin-bottom:12px}
.chapter li{margin-bottom:4px;color:var(--text-body)}
.chapter li strong{color:var(--text-bright)}
.chapter strong{color:var(--text-bright)}
.chapter hr{border:none;border-top:1px solid var(--border);margin:32px 0}

/* ===== BLOCKQUOTE ===== */
blockquote{
  margin:16px 0;padding:12px 16px;border-left:3px solid var(--yc-orange);
  background:var(--yc-glow);border-radius:0 3px 3px 0;font-style:italic;color:var(--text-body);font-size:0.9rem;
}

/* ===== TABLES ===== */
.table-wrap{overflow-x:auto;margin:12px 0;border:1px solid var(--border)}
table{width:100%;border-collapse:collapse;font-size:0.82rem}
th{
  background:var(--bg-elevated);color:var(--yc-orange);font-family:var(--font-heading);
  font-weight:600;font-size:0.76rem;text-align:left;text-transform:uppercase;
  letter-spacing:0.05em;padding:9px 14px;border-bottom:1px solid var(--yc-border);
}
td{padding:8px 14px;border-bottom:1px solid var(--border);color:var(--text-body);font-size:0.8rem}
tr:hover td{background:rgba(255,102,0,0.03)}

/* ===== CODE ===== */
code{
  font-family:var(--font-mono);font-size:0.82em;background:var(--bg-code);
  color:var(--terminal);padding:2px 5px;border-radius:2px;border:1px solid var(--border);
}
pre{
  background:var(--bg-code);border:1px solid var(--border);border-left:3px solid var(--terminal-dim);
  padding:16px;overflow-x:auto;margin:12px 0;position:relative;
}
pre code{background:transparent;padding:0;color:#c0c0c0;font-size:0.78rem;line-height:1.6;border:none}

/* ===== SKILL CARDS ===== */
.skill-card{
  background:var(--bg-surface);border:1px solid var(--border);border-left:3px solid var(--yc-orange);
  padding:20px;margin:16px 0;transition:var(--transition);
}
.skill-card:hover{border-color:var(--yc-border);box-shadow:0 2px 20px rgba(255,102,0,0.05)}
.skill-card h4{margin-top:0;color:var(--yc-orange)}
.skill-card .mode-tag{
  display:inline-block;padding:2px 8px;font-family:var(--font-mono);font-size:0.65rem;
  color:var(--terminal);background:var(--terminal-glow);border:1px solid rgba(57,255,20,0.15);
  letter-spacing:0.04em;text-transform:uppercase;margin-bottom:8px;border-radius:2px;
}

/* ===== BADGE ===== */
.badge{
  display:inline-block;padding:2px 7px;border-radius:2px;font-family:var(--font-mono);
  font-size:0.66rem;font-weight:500;background:var(--yc-glow);color:var(--yc-orange);
  border:1px solid var(--yc-border);letter-spacing:0.04em;
}
.badge.green{background:var(--terminal-glow);color:var(--terminal-dim);border-color:rgba(46,204,64,0.2)}

/* ===== JUMP TOP ===== */
#jump-top{
  position:fixed;bottom:22px;right:22px;width:38px;height:38px;
  background:var(--bg-surface);color:var(--yc-orange);border:1px solid var(--yc-border);
  font-family:var(--font-mono);font-size:1rem;cursor:pointer;
  display:none;align-items:center;justify-content:center;transition:var(--transition);z-index:200;
}
#jump-top:hover{background:var(--yc-glow);border-color:var(--yc-orange);transform:translateY(-2px)}
#jump-top.visible{display:flex}

/* ===== HAMBURGER ===== */
.hamburger{
  display:none;position:fixed;top:8px;left:8px;width:44px;height:44px;z-index:200;
  background:var(--bg-surface);border:1px solid var(--border);cursor:pointer;
  flex-direction:column;align-items:center;justify-content:center;gap:5px;
}
.hamburger span{display:block;width:18px;height:1.5px;background:var(--yc-orange);transition:var(--transition)}
.sidebar-overlay{display:none;position:fixed;inset:0;background:rgba(12,12,12,0.8);z-index:90;backdrop-filter:blur(3px)}

/* ===== RESPONSIVE ===== */
@media(max-width:800px){
  .sidebar{transform:translateX(-100%);width:260px;z-index:150}
  .sidebar.open{transform:translateX(0)}
  .sidebar-overlay.open{display:block}
  .hamburger{display:flex}
  .author-bar{left:0;padding:0 14px;justify-content:center}
  .main-content{margin-left:0;padding:calc(var(--header-h) + 14px) 16px 60px}
  .hero h1{font-size:1.7rem}
  .hero .stats{gap:8px}
  .hero .stat{padding:10px 14px}
  .hero .stat .num{font-size:1.2rem}
  table{font-size:0.74rem}
  th,td{padding:6px 10px}
  #jump-top{bottom:14px;right:14px}
  .chapter>h2{font-size:1.35rem}
}
@media(max-width:375px){
  .main-content{padding-left:12px;padding-right:12px}
  .hero h1{font-size:1.4rem}
}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar{width:5px}
::-webkit-scrollbar-track{background:transparent}
::-webkit-scrollbar-thumb{background:var(--border);border-radius:2px}
::-webkit-scrollbar-thumb:hover{background:var(--text-muted)}

@keyframes fadeIn{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:translateY(0)}}
::selection{background:rgba(255,102,0,0.25);color:var(--text-bright)}