/* ── BLOG BASE ─────────────────────────────────────────────────────────────
   Shared by every blog page: reset, site tokens, nav, toggles, footer.
   Site mode = these tokens. Reader mode overrides them in reader.css.     */

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--nav-h) + 24px); -webkit-text-size-adjust: 100%; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

:root {
  --bg:          #080C14;
  --surface:     #0D1220;
  --surface-2:   #121A2E;
  --surface-3:   #18223C;
  --border:      #1C2840;
  --border-2:    #253352;
  --text:        #DDE4F0;
  --text-muted:  #7E92B8;
  --text-dim:    #3D4F72;
  --text-meta:   #6E82AA;
  --amber:       #F0A030;
  --amber-dim:   #8A5A10;
  --amber-glow:  rgba(240,160,48,0.12);
  --teal:        #22C9A0;
  --teal-dim:    rgba(34,201,160,0.1);
  --link:        var(--amber);
  --nav-bg:      rgba(8,12,20,0.85);

  --font-display:'Fraunces', Georgia, serif;
  --font-mono:   'JetBrains Mono', 'Courier New', monospace;
  --font-body:   'DM Sans', system-ui, sans-serif;
  --font-reading:var(--font-body);
  --font-meta:   var(--font-mono);

  --post-size:   1rem;
  --post-lh:     1.8;
  --measure:     720px;
  --h1-weight:   300;

  --radius:      6px;
  --radius-lg:   12px;
  --max-w:       1120px;
  --nav-h:       64px;

  /* Diagram accents (Mermaid classDefs) */
  --d-green:  #34D399;
  --d-red:    #F87171;
  --d-violet: #A78BFA;
  --d-blue:   #60A5FA;
  --d-gray:   #9CA3AF;

  /* Syntax highlighting */
  --c-text:    #DDE4F0;
  --c-comment: #6E82AA;
  --c-keyword: #F0A030;
  --c-string:  #22C9A0;
  --c-number:  #E0A3F5;
  --c-name:    #8FB8FF;
  --c-key:     #F2C46D;
  --c-punct:   #7E92B8;
}

[data-theme="light"] {
  --bg:          #F5F5F0;
  --surface:     #EEEEE8;
  --surface-2:   #E5E5DF;
  --surface-3:   #DDDDD7;
  --border:      #D0D0C8;
  --border-2:    #B8B8AE;
  --text:        #1A1A2E;
  --text-muted:  #4A4A5E;
  --text-dim:    #8A8A9E;
  --text-meta:   #64647A;
  --amber:       #C07820;
  --amber-dim:   #D4A060;
  --amber-glow:  rgba(192,120,32,0.10);
  --teal:        #0E8A6E;
  --teal-dim:    rgba(14,138,110,0.08);
  --link:        #9A5E12;
  --nav-bg:      rgba(245,245,240,0.85);

  --d-green:  #15803D;
  --d-red:    #B91C1C;
  --d-violet: #6D28D9;
  --d-blue:   #1D4ED8;
  --d-gray:   #6B7280;

  --c-text:    #1A1A2E;
  --c-comment: #6A6A7E;
  --c-keyword: #A0560A;
  --c-string:  #0B7558;
  --c-number:  #8B3FA8;
  --c-name:    #1F55B8;
  --c-key:     #8A4B00;
  --c-punct:   #55556A;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}
main { flex: 1; }
a { color: inherit; text-decoration: none; }
.container { max-width: var(--max-w); margin: 0 auto; padding: 0 32px; }
:focus-visible { outline: 2px solid var(--amber); outline-offset: 3px; border-radius: 3px; }

.skip-link {
  position: absolute; left: 16px; top: -48px; z-index: 200;
  background: var(--surface-2); color: var(--text);
  padding: 8px 14px; border-radius: var(--radius); font-size: 0.875rem;
}
.skip-link:focus { top: 12px; }

/* ── Progress bar ──────────────────────────────────────────────────────── */
.progress { position: fixed; top: 0; left: 0; right: 0; height: 3px; z-index: 150; pointer-events: none; }
.progress-bar { height: 100%; width: 100%; background: var(--amber); transform: scaleX(0); transform-origin: 0 50%; }

/* ── Nav (fixed px: chrome doesn't follow the text-size setting) ────── */
.site-nav {
  position: fixed; top: 0; left: 0; right: 0;
  height: var(--nav-h);
  display: flex; align-items: center;
  background: var(--nav-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid transparent;
  z-index: 100;
  transition: border-color 0.3s, transform 0.3s ease;
}
.site-nav.scrolled { border-color: var(--border); }
.nav-inner { display: flex; align-items: center; width: 100%; }
.nav-logo {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 600;
  color: var(--text);
  margin-right: auto;
}
.nav-logo span { color: var(--amber); }
.nav-links { list-style: none; display: flex; gap: 28px; }
.nav-links a {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--text-muted);
  transition: color 0.2s;
}
.nav-links a:hover, .nav-links a.active { color: var(--amber); }

.mode-toggle, .theme-toggle {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-muted);
  cursor: pointer;
  display: inline-flex; align-items: center; justify-content: center;
  transition: border-color 0.2s, color 0.2s, background 0.2s;
}
.mode-toggle:hover, .theme-toggle:hover { border-color: var(--amber); color: var(--amber); }

.site-nav .text-size { margin-left: 28px; }
.mode-toggle {
  height: 36px; padding: 0 10px 0 12px; gap: 8px;
  border-radius: 18px;
  margin-left: 10px;
  font-family: var(--font-mono);
  font-size: 12px;
}
.mode-icon { flex: none; }
.mode-switch {
  position: relative; width: 26px; height: 16px; border-radius: 8px;
  background: var(--border-2); transition: background 0.2s;
}
.mode-switch::after {
  content: ""; position: absolute; top: 2px; left: 2px;
  width: 12px; height: 12px; border-radius: 50%;
  background: var(--bg); transition: transform 0.2s;
}
.mode-toggle[aria-pressed="true"] { color: var(--text); }
.mode-toggle[aria-pressed="true"] .mode-switch { background: var(--amber); }
.mode-toggle[aria-pressed="true"] .mode-switch::after { transform: translateX(10px); }

.theme-toggle {
  border-radius: 50%; width: 36px; height: 36px;
  margin-left: 12px; font-size: 16px;
}
.icon-sun { display: none; }
[data-theme="light"] .icon-moon { display: none; }
[data-theme="light"] .icon-sun { display: inline; }

.hamburger { display: none; background: none; border: none; cursor: pointer; padding: 8px; margin-left: 8px; }
.hamburger span { display: block; width: 20px; height: 2px; background: var(--text-muted); margin: 4px 0; transition: all 0.3s; }

@media (max-width: 768px) {
  .container { padding: 0 16px; }
  .nav-links { display: none; position: fixed; top: var(--nav-h); left: 0; right: 0; background: var(--bg); flex-direction: column; align-items: center; padding: 24px 0; gap: 20px; border-bottom: 1px solid var(--border); }
  .nav-links.open { display: flex; }
  .hamburger { display: block; }
  .hamburger.active span:nth-child(1) { transform: rotate(45deg) translate(4px, 4px); }
  .hamburger.active span:nth-child(2) { opacity: 0; }
  .hamburger.active span:nth-child(3) { transform: rotate(-45deg) translate(4px, -4px); }
  .site-nav .text-size { margin-left: 0; }
  .mode-toggle { margin-left: 8px; }
  .theme-toggle { margin-left: 8px; }
}
@media (max-width: 380px) {
  .mode-label { display: none; }
}

/* ── Footer ────────────────────────────────────────────────────────────── */
.site-footer { border-top: 1px solid var(--border); padding: 32px 0; margin-top: 40px; }
.site-footer-inner { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 16px; }
.site-footer-copy { font-family: var(--font-mono); font-size: 0.8125rem; color: var(--text-meta); }
.site-footer-links { display: flex; gap: 20px; flex-wrap: wrap; }
.site-footer-links a { font-family: var(--font-mono); font-size: 0.8125rem; color: var(--text-muted); transition: color 0.2s; }
.site-footer-links a:hover { color: var(--amber); }

/* ── Reader-mode notice (once per session) ─────────────────────────────── */
.reader-tip {
  position: fixed;
  z-index: 140;
  width: min(300px, calc(100vw - 24px));
  padding: 12px 14px;
  background: var(--surface-2);
  color: var(--text);
  border: 1px solid var(--amber-dim);
  border-radius: var(--radius-lg);
  box-shadow: 0 14px 36px rgba(0, 0, 0, 0.32);
  font-family: var(--font-body);
  font-size: 13.5px;
  line-height: 1.45;
  pointer-events: none;           /* never blocks clicks or scrolling */
  opacity: 0;
  transform: translateY(-6px);
  transition: opacity 0.25s ease, transform 0.25s ease;
}
.reader-tip.is-visible { opacity: 1; transform: none; }
.reader-tip strong { display: block; font-weight: 600; color: var(--amber); margin-bottom: 2px; }
.reader-tip-arrow {
  position: absolute;
  top: -7px;
  width: 12px; height: 12px;
  margin-left: -6px;
  background: var(--surface-2);
  border-left: 1px solid var(--amber-dim);
  border-top: 1px solid var(--amber-dim);
  transform: rotate(45deg);
}
.mode-toggle.is-hinting { box-shadow: 0 0 0 3px var(--amber-glow), 0 0 0 1px var(--amber); border-color: var(--amber); }
@media (prefers-reduced-motion: reduce) {
  .reader-tip { transition: opacity 0.2s; transform: none; }
}