/* ── Variables ──────────────────────────────────────── */
:root {
  --bg:         #F8F9FA;
  --bg-card:    #FFFFFF;
  --bg-nav:     rgba(248, 249, 250, 0.88);
  --text:       #111827;
  --text-sub:   #4B5563;
  --text-muted: #9CA3AF;
  --accent:     #2563EB;
  --accent-soft:#EFF6FF;
  --border:     #E5E7EB;
  --timeline:   #D1D5DB;
  --badge-bg:   #F3F4F6;
  --badge-text: #374151;
  --shadow:     0 1px 3px rgba(0,0,0,0.07), 0 4px 16px rgba(0,0,0,0.04);
  --radius:     10px;
  --t:          0.22s ease;
}
[data-theme="dark"] {
  --bg:         #0F1117;
  --bg-card:    #1A1D27;
  --bg-nav:     rgba(15, 17, 23, 0.9);
  --text:       #F1F5F9;
  --text-sub:   #94A3B8;
  --text-muted: #64748B;
  --accent:     #60A5FA;
  --accent-soft:#1E3A5F;
  --border:     #2D3140;
  --timeline:   #374151;
  --badge-bg:   #1E2130;
  --badge-text: #CBD5E1;
  --shadow:     0 1px 4px rgba(0,0,0,0.3), 0 4px 20px rgba(0,0,0,0.2);
}

/* ── Reset ──────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  transition: background var(--t), color var(--t);
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
ul { list-style: none; }

/* ── Layout ─────────────────────────────────────────── */
.container { max-width: 780px; margin: 0 auto; padding: 0 24px; }
main { padding-top: 90px; padding-bottom: 80px; }

/* ── Nav ─────────────────────────────────────────────── */
nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: var(--bg-nav);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
  transition: background var(--t), border-color var(--t);
}
.nav-inner {
  max-width: 780px; margin: 0 auto; padding: 0 24px;
  height: 54px; display: flex; align-items: center;
  justify-content: space-between; gap: 12px;
}
.nav-logo {
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-weight: 700;
  font-size: 0.92rem; letter-spacing: 0.02em;
  color: var(--text); white-space: nowrap; flex-shrink: 0;
}
.nav-links {
  display: flex; align-items: center; gap: 2px;
  overflow-x: auto; scrollbar-width: none;
}
.nav-links::-webkit-scrollbar { display: none; }
.nav-links a {
  font-size: 0.7rem; font-weight: 500; color: var(--text-sub);
  padding: 4px 8px; border-radius: 6px; white-space: nowrap;
  transition: color var(--t), background var(--t);
}
.nav-links a:hover, .nav-links a.active {
  color: var(--accent); background: var(--accent-soft);
  text-decoration: none;
}

/* ── Nav back (post pages) ───────────────────────────── */
.nav-back {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 0.82rem; font-weight: 500; color: var(--text-sub);
  transition: color var(--t);
}
.nav-back:hover { color: var(--accent); text-decoration: none; }
.nav-back svg { width: 14px; height: 14px; }

/* ── Theme toggle ────────────────────────────────────── */
.toggle-wrap { display: flex; align-items: center; gap: 7px; flex-shrink: 0; }
.toggle-icon { font-size: 0.82rem; user-select: none; }
.theme-toggle {
  width: 38px; height: 21px; background: var(--border);
  border-radius: 11px; border: none; cursor: pointer;
  position: relative; transition: background var(--t); outline: none;
}
.theme-toggle::after {
  content: ''; position: absolute; top: 2px; left: 2px;
  width: 17px; height: 17px; border-radius: 50%;
  background: var(--bg-card); box-shadow: 0 1px 4px rgba(0,0,0,0.2);
  transition: transform 0.22s cubic-bezier(0.4,0,0.2,1), background var(--t);
}
[data-theme="dark"] .theme-toggle { background: var(--accent); }
[data-theme="dark"] .theme-toggle::after { transform: translateX(17px); }

/* ── Fade-up ─────────────────────────────────────────── */
.fade-up { opacity: 0; transform: translateY(18px); transition: opacity 0.48s ease, transform 0.48s ease; }
.fade-up.visible { opacity: 1; transform: none; }

/* ── Cards ───────────────────────────────────────────── */
.card-list { display: flex; flex-direction: column; gap: 14px; }
.card-list-2col { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; }
@media (max-width: 620px) { .card-list-2col { grid-template-columns: 1fr; } }
.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow);
  transition: background var(--t), border-color var(--t);
}
.card:hover { border-color: var(--accent); }
.card-header { display: flex; justify-content: space-between; align-items: flex-start; flex-wrap: wrap; gap: 6px; margin-bottom: 4px; }
.card-title { font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 0.92rem; font-weight: 700; }
.card-date { font-family: 'JetBrains Mono', monospace; font-size: 0.67rem; color: var(--text-muted); white-space: nowrap; padding-top: 3px; }
.card-sub { font-size: 0.78rem; color: var(--accent); font-weight: 500; margin-bottom: 8px; }
.card-tags { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 10px; }
.card-tag {
  font-family: 'JetBrains Mono', monospace; font-size: 0.65rem;
  padding: 2px 8px; border-radius: 4px;
  background: var(--accent-soft); color: var(--accent);
  border: 1px solid var(--accent); letter-spacing: 0.02em;
}
.card-company { font-size: 0.78rem; color: var(--text-muted); font-weight: 500; }
.card-desc { font-size: 0.82rem; color: var(--text-sub); line-height: 1.7; }
.card-desc li { padding-left: 12px; position: relative; margin-bottom: 2px; }
.card-desc li::before { content: '·'; position: absolute; left: 0; color: var(--accent); font-weight: 700; }
.card-link { display: inline-block; margin-top: 8px; font-size: 0.75rem; font-weight: 500; }

/* ── Footer ──────────────────────────────────────────── */
footer {
  text-align: center; padding: 28px 24px;
  font-family: 'JetBrains Mono', monospace; font-size: 0.7rem;
  color: var(--text-muted); border-top: 1px solid var(--border);
}

/* ── Responsive ──────────────────────────────────────── */
@media (max-width: 620px) {
  .nav-links { display: none; }
}