/* ==========================================================================
   bec.usmc.help — Tactical High-Performance Stylesheet
   Design Philosophy: Marines.mil-inspired authoritative typography,
   pure-black OLED / pure-white contrast, zero-clutter, mobile-first UX.
   ========================================================================== */

/* --------------------------------------------------------------------------
   Design Tokens & Color Engine
   -------------------------------------------------------------------------- */
:root {
  --bg-primary: #000000;
  --bg-secondary: #0a0a0a;
  --bg-tertiary: #141414;
  --bg-card: #0d0d0d;
  
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  
  --border-color: #22262e;
  --border-hover: #3b4252;
  --border-strong: #4c566a;
  
  --usmc-scarlet: #b91c1c;
  --usmc-scarlet-glow: rgba(185, 28, 28, 0.25);
  --usmc-gold: #c59b27;
  --usmc-gold-muted: rgba(197, 155, 39, 0.2);
  
  --nav-btn-bg: #0f1115;
  --nav-btn-border: #2d333f;
  --nav-btn-hover-bg: #1a1e27;
  --nav-btn-hover-border: #94a3b8;
  
  --code-bg: #0d1117;
  --code-border: #21262d;
  --table-header-bg: #0f131a;
  --table-stripe: #07090c;
  
  --alert-note: #2563eb;
  --alert-warning: #d97706;
  --alert-important: #dc2626;
  --alert-tip: #059669;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  
  --transition-fast: 0.12s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-smooth: 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

[data-theme="light"] {
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --bg-card: #f8fafc;
  
  --text-primary: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  
  --border-color: #e2e8f0;
  --border-hover: #cbd5e1;
  --border-strong: #94a3b8;
  
  --usmc-scarlet: #991b1b;
  --usmc-scarlet-glow: rgba(153, 27, 27, 0.12);
  --usmc-gold: #9a7318;
  --usmc-gold-muted: rgba(154, 115, 24, 0.15);
  
  --nav-btn-bg: #f8fafc;
  --nav-btn-border: #cbd5e1;
  --nav-btn-hover-bg: #f1f5f9;
  --nav-btn-hover-border: #64748b;
  
  --code-bg: #f1f5f9;
  --code-border: #e2e8f0;
  --table-header-bg: #f1f5f9;
  --table-stripe: #f8fafc;
}

/* --------------------------------------------------------------------------
   Reset & Baseline
   -------------------------------------------------------------------------- */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.68;
  letter-spacing: -0.006em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* --------------------------------------------------------------------------
   Authoritative Top Navigation (Marines.mil inspired precision)
   -------------------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

/* Subtle tactical dual-accent hairline */
.site-header::before {
  content: "";
  display: block;
  height: 2px;
  width: 100%;
  background: linear-gradient(90deg, var(--usmc-scarlet) 0%, var(--usmc-scarlet) 60%, var(--usmc-gold) 60%, var(--usmc-gold) 100%);
}

.header-container {
  max-width: 960px;
  margin: 0 auto;
  padding: 10px 20px;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 12px;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 6px;
}

.header-nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 8px 14px;
  border-radius: 4px;
  border: 1px solid transparent;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.header-nav a:hover {
  color: var(--text-primary);
  background: var(--bg-secondary);
  border-color: var(--border-color);
}

.header-nav a.btn-active {
  color: var(--text-primary);
  background: var(--bg-secondary);
  border-color: var(--border-hover);
}

/* Theme Toggle Button (Vector SVG, No Emojis) */
.theme-toggle-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 38px;
  height: 38px;
  border-radius: 4px;
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  cursor: pointer;
  padding: 0;
  transition: all var(--transition-fast);
}

.theme-toggle-btn:hover {
  color: var(--text-primary);
  background: var(--bg-secondary);
  border-color: var(--border-strong);
  transform: translateY(-1px);
}

.theme-toggle-btn:active {
  transform: translateY(0);
}

.theme-icon {
  width: 18px;
  height: 18px;
  stroke-width: 2;
  transition: transform var(--transition-smooth);
}

[data-theme="dark"] .theme-icon-sun {
  display: block;
}
[data-theme="dark"] .theme-icon-moon {
  display: none;
}

[data-theme="light"] .theme-icon-sun {
  display: none;
}
[data-theme="light"] .theme-icon-moon {
  display: block;
}

/* --------------------------------------------------------------------------
   Main Content Layout
   -------------------------------------------------------------------------- */
.main-wrapper {
  max-width: 960px;
  width: 100%;
  margin: 0 auto;
  padding: 44px 24px 90px;
  flex: 1 0 auto;
}

.content-body {
  width: 100%;
}

/* --------------------------------------------------------------------------
   Typography Hierarchy
   -------------------------------------------------------------------------- */
.content-body h1,
.content-body h2,
.content-body h3,
.content-body h4 {
  color: var(--text-primary);
  font-family: var(--font-sans);
  text-transform: uppercase;
  letter-spacing: 0.03em;
  line-height: 1.25;
}

.content-body h1 {
  font-size: clamp(1.8rem, 4vw, 2.3rem);
  font-weight: 800;
  margin-top: 0;
  margin-bottom: 24px;
  padding-bottom: 14px;
  border-bottom: 2px solid var(--border-color);
  letter-spacing: 0.02em;
}

.content-body h2 {
  font-size: clamp(1.3rem, 2.5vw, 1.55rem);
  font-weight: 700;
  margin-top: 48px;
  margin-bottom: 18px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}

.content-body h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-top: 32px;
  margin-bottom: 12px;
  color: var(--text-primary);
}

.content-body h4 {
  font-size: 0.95rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  margin-top: 24px;
  margin-bottom: 8px;
  color: var(--text-secondary);
}

.content-body p {
  margin-bottom: 1.3em;
  color: var(--text-primary);
  font-size: 1rem;
}

.content-body ul,
.content-body ol {
  margin-left: 24px;
  margin-bottom: 1.5em;
}

.content-body li {
  margin-bottom: 0.5em;
  padding-left: 4px;
}

.content-body strong {
  font-weight: 700;
  color: var(--text-primary);
}

.content-body a {
  color: var(--text-primary);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  transition: color var(--transition-fast);
}

.content-body a:hover {
  color: var(--usmc-gold);
}

.content-body hr {
  border: none;
  border-top: 1px solid var(--border-color);
  margin: 48px 0;
}

/* --------------------------------------------------------------------------
   Tactical Navigation Buttons (.nav-button)
   -------------------------------------------------------------------------- */
.nav-button,
a.nav-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 20px;
  background: var(--nav-btn-bg);
  border: 1px solid var(--nav-btn-border);
  border-radius: 4px;
  color: var(--text-primary) !important;
  text-decoration: none !important;
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin: 6px 10px 8px 0;
  min-height: 46px;
  transition: all var(--transition-fast);
  cursor: pointer;
}

.nav-button:hover,
a.nav-button:hover {
  background: var(--nav-btn-hover-bg);
  border-color: var(--nav-btn-hover-border);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
}

.nav-button:active,
a.nav-button:active {
  transform: translateY(0);
}

/* --------------------------------------------------------------------------
   Responsive Tactical Tables
   -------------------------------------------------------------------------- */
.table-container {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 28px 0;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  background: var(--bg-card);
}

table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.9rem;
}

th, td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-color);
  vertical-align: middle;
}

th {
  background: var(--table-header-bg);
  font-weight: 700;
  color: var(--text-secondary);
  text-transform: uppercase;
  font-size: 0.74rem;
  letter-spacing: 0.08em;
  border-bottom: 2px solid var(--border-strong);
  white-space: nowrap;
}

tr:nth-child(even) td {
  background: var(--table-stripe);
}

tr:last-child td {
  border-bottom: none;
}

/* --------------------------------------------------------------------------
   Code, Math & Callouts
   -------------------------------------------------------------------------- */
code {
  font-family: var(--font-mono);
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  padding: 2px 6px;
  border-radius: 3px;
  font-size: 0.88em;
  color: var(--text-primary);
  word-break: break-word;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  padding: 18px;
  border-radius: 4px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin-bottom: 1.5em;
}

pre code {
  background: transparent;
  border: none;
  padding: 0;
}

blockquote {
  border-left: 4px solid var(--border-strong);
  background: var(--bg-secondary);
  padding: 14px 18px;
  margin: 20px 0;
  border-radius: 0 4px 4px 0;
  color: var(--text-secondary);
  font-style: normal;
}

/* Alert Boxes */
.alert {
  padding: 14px 18px;
  margin: 22px 0;
  border-left: 4px solid var(--border-strong);
  background: var(--bg-secondary);
  border-radius: 0 4px 4px 0;
  font-size: 0.95rem;
}

.alert-note {
  border-left-color: var(--alert-note);
}
.alert-warning {
  border-left-color: var(--alert-warning);
}
.alert-important {
  border-left-color: var(--alert-important);
}
.alert-tip {
  border-left-color: var(--alert-tip);
}

.alert strong {
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-size: 0.84rem;
  margin-right: 6px;
}

/* KaTeX Display Math Container (Fluid Mobile Scroll) */
.katex-display-block {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  padding: 12px 0;
  margin: 18px 0;
}

.katex {
  font-size: 1.08em;
}

/* --------------------------------------------------------------------------
   Inline SVG Schematics
   -------------------------------------------------------------------------- */
svg.schematic-svg {
  max-width: 100%;
  height: auto;
  margin: 24px auto;
  display: block;
}

[data-theme="dark"] svg.schematic-svg path,
[data-theme="dark"] svg.schematic-svg circle,
[data-theme="dark"] svg.schematic-svg rect,
[data-theme="dark"] svg.schematic-svg line {
  stroke: #ffffff !important;
}

[data-theme="dark"] svg.schematic-svg text {
  fill: #ffffff !important;
}

/* --------------------------------------------------------------------------
   Site Footer
   -------------------------------------------------------------------------- */
.site-footer {
  border-top: 1px solid var(--border-color);
  padding: 36px 20px 48px;
  text-align: center;
  font-size: 0.82rem;
  color: var(--text-muted);
  background: var(--bg-secondary);
}

.site-footer a {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  transition: color var(--transition-fast);
}

.site-footer a:hover {
  color: var(--text-primary);
}

/* --------------------------------------------------------------------------
   Mobile-First Media Queries (Touchscreen Optimization)
   -------------------------------------------------------------------------- */
@media (max-width: 768px) {
  .header-container {
    padding: 8px 16px;
    gap: 8px;
  }

  .header-nav a {
    font-size: 0.74rem;
    padding: 8px 10px;
    letter-spacing: 0.05em;
  }

  .main-wrapper {
    padding: 24px 16px 64px;
  }

  .content-body h1 {
    font-size: 1.65rem;
    margin-bottom: 18px;
    padding-bottom: 10px;
  }

  .content-body h2 {
    font-size: 1.25rem;
    margin-top: 36px;
    margin-bottom: 14px;
  }

  .nav-button,
  a.nav-button {
    display: flex;
    width: 100%;
    margin: 8px 0;
    text-align: center;
    padding: 14px 16px;
    font-size: 0.8rem;
  }

  th, td {
    padding: 10px 12px;
    font-size: 0.84rem;
  }
}

@media (max-width: 480px) {
  .header-nav {
    width: 100%;
    justify-content: flex-end;
  }

  .content-body p,
  .content-body li {
    font-size: 0.95rem;
    line-height: 1.62;
  }
}