/* ==========================================================
   6686中国官网 — 全站共享样式 /assets/site.css
   设计基因：框架导航、切角面板、技术文档感、滚动轨迹
   ========================================================== */

/* ---------- 01. Design Tokens ---------- */
:root {
  --color-blue: #0B1B2B;
  --color-blue-light: #1A2B4C;
  --color-orange: #FF6B2C;
  --color-orange-light: #FFD1B3;
  --color-silver: #A8B2C1;
  --color-white: #F5F7FA;
  --color-dark: #0A0E13;
  --color-blue-gray: #6B7A8D;

  --font-heading: Inter, "PingFang SC", "Microsoft YaHei", sans-serif;
  --font-body: "JetBrains Mono", "Roboto Mono", "Courier New", monospace;

  --size-display: clamp(48px, 8vw, 120px);
  --size-heading: clamp(24px, 4vw, 48px);
  --size-subheading: clamp(18px, 2vw, 24px);
  --size-body: 16px;
  --size-caption: 12px;

  --container: 1240px;
  --gutter: 24px;

  --space-xxs: 4px;
  --space-xs: 8px;
  --space-sm: 16px;
  --space-md: 32px;
  --space-lg: 64px;
  --space-xl: 120px;

  --cut-size: 18px;
  --border-faint: rgba(168, 178, 193, 0.15);
  --border-mid: rgba(168, 178, 193, 0.3);

  --ease-fast: 200ms ease;
  --ease-medium: 300ms ease;
}

/* ---------- 02. Reset & Base ---------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  -webkit-text-size-adjust: 100%;
}

@media (prefers-reduced-motion: no-preference) {
  html {
    scroll-behavior: smooth;
  }
}

body {
  min-height: 100vh;
  font-family: var(--font-body);
  font-size: var(--size-body);
  line-height: 1.75;
  color: var(--color-silver);
  background-color: var(--color-blue);
  background-image:
    linear-gradient(rgba(168, 178, 193, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(168, 178, 193, 0.035) 1px, transparent 1px);
  background-size: 32px 32px;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

#main-content {
  display: block;
  min-height: 65vh;
  scroll-margin-top: 88px;
}

/* ---------- 03. Typography ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  line-height: 1.25;
  color: var(--color-white);
  font-weight: 700;
  margin-bottom: 0.5em;
}

h1 {
  font-size: var(--size-display);
  font-weight: 900;
  letter-spacing: -0.03em;
}

h2 {
  font-size: var(--size-heading);
  letter-spacing: -0.01em;
}

h3 {
  font-size: var(--size-subheading);
  font-weight: 500;
}

h4 {
  font-size: 18px;
  font-weight: 600;
}

p {
  margin-bottom: 1em;
}

small {
  font-size: var(--size-caption);
}

a {
  color: var(--color-orange);
  text-decoration: none;
  transition: color var(--ease-fast);
}

a:hover {
  color: var(--color-orange-light);
}

ul, ol {
  padding-left: 1.4em;
  margin-bottom: 1em;
}

li {
  margin-bottom: 0.4em;
}

blockquote {
  border-left: 3px solid var(--color-orange);
  padding-left: var(--space-sm);
  color: var(--color-white);
  margin: var(--space-md) 0;
}

::selection {
  background: var(--color-orange);
  color: var(--color-dark);
}

:focus-visible {
  outline: 2px solid var(--color-orange);
  outline-offset: 3px;
}

/* ---------- 04. Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 22px;
  font-family: var(--font-heading);
  font-size: 15px;
  font-weight: 600;
  line-height: 1.2;
  text-decoration: none;
  border: 1px solid transparent;
  cursor: pointer;
  background: none;
  position: relative;
  transition: background-color var(--ease-fast), color var(--ease-fast), border-color var(--ease-fast), transform var(--ease-fast);
}

.btn:focus-visible {
  outline: 2px solid var(--color-orange);
  outline-offset: 3px;
}

.btn-primary {
  background: var(--color-orange);
  color: var(--color-dark);
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 12px 100%, 0 calc(100% - 12px));
}

.btn-primary:hover {
  background: var(--color-orange-light);
  color: var(--color-dark);
}

.btn-primary:focus-visible {
  outline: none;
  box-shadow: inset 0 0 0 2px var(--color-white);
}

.btn-secondary {
  background: transparent;
  border-color: var(--color-silver);
  color: var(--color-white);
}

.btn-secondary:hover {
  border-color: var(--color-orange);
  color: var(--color-orange);
}

.btn-ghost {
  background: transparent;
  color: var(--color-silver);
  padding-left: 8px;
  padding-right: 8px;
}

.btn-ghost:hover {
  color: var(--color-orange);
}

/* ---------- 05. Skip Link ---------- */
.skip-link {
  position: fixed;
  top: 0;
  left: var(--gutter);
  z-index: 600;
  padding: 10px 18px;
  background: var(--color-orange);
  color: var(--color-dark);
  font-family: var(--font-heading);
  font-size: 14px;
  font-weight: 700;
  text-decoration: none;
  transform: translateY(-120%);
  transition: transform var(--ease-fast);
}

.skip-link:focus {
  transform: translateY(0);
  outline: 2px solid var(--color-white);
  outline-offset: -2px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.4);
}

/* ---------- 06. Site Frame (Header) ---------- */
.site-frame {
  position: sticky;
  top: 0;
  z-index: 200;
  background: rgba(11, 27, 43, 0.94);
  -webkit-backdrop-filter: blur(10px);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-faint);
}

.frame-progress {
  position: absolute;
  top: 0;
  left: 0;
  height: 4px;
  width: 100%;
  background: var(--color-orange);
  transform: scaleX(0.15);
  transform-origin: left center;
  z-index: 6;
  will-change: transform;
}

.frame-bar {
  position: relative;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--gutter);
  display: flex;
  align-items: center;
  gap: var(--space-md);
  height: 78px;
}

.brand-lockup {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  text-decoration: none;
  flex-shrink: 0;
}

.brand-lockup:hover .brand-code,
.brand-lockup:hover .brand-name {
  color: var(--color-orange-light);
}

.brand-code {
  font-family: var(--font-heading);
  font-size: 30px;
  font-weight: 900;
  letter-spacing: 0.04em;
  color: var(--color-white);
  line-height: 1;
  transition: color var(--ease-fast);
}

.brand-name {
  font-family: var(--font-heading);
  font-size: 19px;
  font-weight: 700;
  color: var(--color-white);
  line-height: 1;
  transition: color var(--ease-fast);
}

.brand-tag {
  font-family: var(--font-body);
  font-size: 11px;
  color: var(--color-blue-gray);
  letter-spacing: 0.14em;
  padding-left: var(--space-sm);
  border-left: 1px solid var(--color-blue-gray);
  line-height: 1.6;
  white-space: nowrap;
}

.frame-nav {
  display: flex;
  align-items: stretch;
  gap: 4px;
  margin: 0 auto;
  height: 100%;
}

.frame-link {
  position: relative;
  display: flex;
  align-items: center;
  padding: 0 14px;
  font-family: var(--font-heading);
  font-size: 15px;
  font-weight: 500;
  color: var(--color-silver);
  text-decoration: none;
  white-space: nowrap;
  transition: color var(--ease-fast);
}

.frame-link::before {
  content: attr(data-index) " /";
  font-family: var(--font-body);
  font-size: 10px;
  color: var(--color-orange);
  opacity: 0.78;
  margin-right: 6px;
  font-weight: 400;
}

.frame-link:hover {
  color: var(--color-white);
}

.frame-link[aria-current="page"] {
  color: var(--color-white);
}

.frame-link[aria-current="page"]::after {
  content: "";
  position: absolute;
  left: 14px;
  right: 14px;
  bottom: 0;
  height: 3px;
  background: var(--color-orange);
}

.frame-cta {
  flex-shrink: 0;
}

/* ---------- 07. Mobile Nav Toggle ---------- */
.frame-toggle {
  display: none;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  background: transparent;
  border: 1px solid var(--color-blue-gray);
  color: var(--color-white);
  font-family: var(--font-heading);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: border-color var(--ease-fast), color var(--ease-fast);
}

.frame-toggle:hover {
  border-color: var(--color-orange);
  color: var(--color-orange);
}

.frame-toggle[aria-expanded="true"] {
  border-color: var(--color-orange);
  color: var(--color-orange);
}

.frame-toggle-box {
  display: inline-flex;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 18px;
  height: 14px;
}

.frame-toggle-line {
  display: block;
  width: 18px;
  height: 2px;
  background: currentColor;
  transition: transform var(--ease-fast), opacity var(--ease-fast);
}

.frame-toggle[aria-expanded="true"] .frame-toggle-line:nth-child(1) {
  transform: translateY(3.5px) rotate(45deg);
}

.frame-toggle[aria-expanded="true"] .frame-toggle-line:nth-child(2) {
  transform: translateY(-3.5px) rotate(-45deg);
}

.frame-toggle-text {
  font-family: var(--font-heading);
  font-size: 13px;
  font-weight: 500;
  color: currentColor;
}

/* ---------- 08. Responsive Header ---------- */
@media (max-width: 1099px) {
  .frame-bar {
    gap: var(--space-sm);
  }

  .frame-link {
    padding: 0 8px;
    font-size: 14px;
  }

  .brand-tag {
    display: none;
  }
}

@media (max-width: 899px) {
  .frame-bar {
    height: 64px;
    gap: var(--space-sm);
  }

  .brand-code {
    font-size: 24px;
  }

  .brand-name {
    font-size: 17px;
  }

  .frame-toggle {
    display: inline-flex;
    margin-left: 0;
  }

  .frame-cta {
    margin-left: auto;
    padding: 8px 14px;
    font-size: 13px;
  }

  .frame-nav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    height: auto;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    margin: 0;
    padding: var(--space-xs) 0 var(--space-sm);
    background: rgba(26, 43, 76, 0.98);
    border-bottom: 1px solid var(--color-blue-gray);
    box-shadow: 0 16px 40px rgba(0, 0, 0, 0.3);
    max-height: calc(100vh - 64px);
    overflow-y: auto;
    visibility: hidden;
    opacity: 0;
    transform: translateY(-8px);
    pointer-events: none;
    transition: opacity var(--ease-medium), transform var(--ease-medium), visibility var(--ease-medium);
  }

  .frame-nav[data-open] {
    visibility: visible;
    opacity: 1;
    transform: translateY(0);
    pointer-events: auto;
  }

  .frame-link {
    min-height: 48px;
    padding: 12px var(--gutter);
    font-size: 17px;
    border-left: 3px solid transparent;
    align-items: center;
  }

  .frame-link::after {
    display: none;
  }

  .frame-link[aria-current="page"] {
    border-left-color: var(--color-orange);
    background: rgba(255, 107, 44, 0.08);
  }
}

@media (max-width: 479px) {
  .frame-toggle-text {
    display: none;
  }
}

@media (max-width: 359px) {
  .frame-cta {
    padding: 8px 10px;
    font-size: 12px;
  }
}

/* ---------- 09. Footer ---------- */
.site-footer {
  background: var(--color-dark);
  color: var(--color-blue-gray);
}

.site-footer::before {
  content: "";
  display: block;
  height: 4px;
  background: linear-gradient(90deg, var(--color-orange) 0%, var(--color-orange-light) 100%);
}

.footer-frame {
  max-width: var(--container);
  margin: 0 auto;
  padding: var(--space-lg) var(--gutter) var(--space-md);
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--space-lg);
  padding-bottom: var(--space-lg);
  border-bottom: 1px solid var(--border-faint);
}

.footer-brand-lockup {
  display: inline-flex;
  align-items: baseline;
  gap: var(--space-xs);
  text-decoration: none;
  margin-bottom: var(--space-sm);
}

.footer-brand-lockup:hover .footer-brand-code,
.footer-brand-lockup:hover .footer-brand-name {
  color: var(--color-orange-light);
}

.footer-brand-code {
  font-family: var(--font-heading);
  font-size: 30px;
  font-weight: 900;
  color: var(--color-white);
  transition: color var(--ease-fast);
}

.footer-brand-name {
  font-family: var(--font-heading);
  font-size: 19px;
  font-weight: 700;
  color: var(--color-white);
  transition: color var(--ease-fast);
}

.footer-about {
  max-width: 300px;
  font-size: 13px;
  line-height: 1.75;
  color: var(--color-blue-gray);
  margin-bottom: var(--space-sm);
}

.footer-contact {
  font-size: 12px;
  line-height: 1.8;
  color: var(--color-blue-gray);
  border-top: 1px solid var(--border-faint);
  padding-top: var(--space-sm);
  max-width: 340px;
}

.footer-title {
  font-family: var(--font-heading);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-white);
  margin-bottom: var(--space-sm);
}

.footer-link {
  display: block;
  font-family: var(--font-heading);
  font-size: 14px;
  color: var(--color-blue-gray);
  text-decoration: none;
  padding: 5px 0;
  transition: color var(--ease-fast), transform var(--ease-fast);
}

.footer-link:hover {
  color: var(--color-orange);
  transform: translateX(2px);
}

.footer-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-sm) var(--space-md);
  padding-top: var(--space-md);
  font-size: 12px;
}

.footer-trust {
  color: var(--color-blue-gray);
  opacity: 0.8;
}

.footer-copy {
  color: var(--color-blue-gray);
}

.footer-icp {
  color: var(--color-blue-gray);
  margin-left: auto;
}

@media (max-width: 899px) {
  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-md);
  }

  .footer-brand-col {
    grid-column: 1 / -1;
  }

  .footer-icp {
    margin-left: inherit;
  }
}

@media (max-width: 559px) {
  .footer-grid {
    grid-template-columns: 1fr;
  }

  .footer-brand-col {
    grid-column: auto;
  }
}

/* ---------- 10. Layout Components ---------- */
.container {
  max-width: var(--container);
  margin: 0 auto;
  padding-left: var(--gutter);
  padding-right: var(--gutter);
}

.section {
  padding: var(--space-xl) 0;
  position: relative;
}

.section:first-child {
  padding-top: var(--space-lg);
}

.section-band {
  position: relative;
  padding: var(--space-lg) 0;
  margin: var(--space-xl) 0;
  background: linear-gradient(90deg, var(--color-blue-light) 0%, rgba(26, 43, 76, 0) 100%);
  border-top: 1px solid var(--color-blue-gray);
  border-bottom: 1px solid var(--color-blue-gray);
}

.section-band::before {
  content: "";
  position: absolute;
  left: 0;
  top: -1px;
  width: 96px;
  height: 3px;
  background: var(--color-orange);
}

.section-band::after {
  content: "";
  position: absolute;
  right: 0;
  bottom: 0;
  width: 24px;
  height: 24px;
  background: var(--color-orange);
  clip-path: polygon(100% 0, 100% 100%, 0 100%);
}

.section-head {
  display: flex;
  align-items: baseline;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.section-head::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--border-faint);
}

.section-index {
  font-family: var(--font-body);
  font-size: 13px;
  font-weight: 700;
  color: var(--color-orange);
  letter-spacing: 0.1em;
  white-space: nowrap;
}

.section-title {
  font-family: var(--font-heading);
  font-size: var(--size-heading);
  font-weight: 700;
  color: var(--color-white);
  margin: 0;
  white-space: nowrap;
}

/* ---------- 11. Grid ---------- */
.grid {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: var(--space-md);
}

.grid > * {
  min-width: 0;
}

.col-3 { grid-column: span 3; }
.col-4 { grid-column: span 4; }
.col-5 { grid-column: span 5; }
.col-6 { grid-column: span 6; }
.col-7 { grid-column: span 7; }
.col-8 { grid-column: span 8; }
.col-12 { grid-column: span 12; }

.grid-split {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-lg);
  align-items: start;
}

.grid-trio {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-md);
}

.grid-collapse {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: var(--space-lg);
  align-items: start;
}

@media (max-width: 899px) {
  .grid > * {
    grid-column: 1 / -1;
  }

  .grid-split,
  .grid-trio,
  .grid-collapse {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }
}

/* ---------- 12. Panels & Study Board ---------- */
.panel {
  background: var(--color-blue-light);
  border: 1px solid var(--border-mid);
  padding: var(--space-md);
  position: relative;
}

.panel-cut {
  clip-path: polygon(0 0, calc(100% - var(--cut-size)) 0, 100% var(--cut-size), 100% 100%, var(--cut-size) 100%, 0 calc(100% - var(--cut-size)));
}

.board {
  background:
    linear-gradient(135deg, rgba(255, 107, 44, 0.06) 0%, rgba(255, 107, 44, 0) 35%),
    var(--color-blue-light);
  border: 1px solid var(--border-mid);
  padding: var(--space-lg);
  position: relative;
  margin-bottom: var(--space-md);
}

.board[data-code]::before {
  content: attr(data-code);
  font-family: var(--font-body);
  font-size: 10px;
  letter-spacing: 0.12em;
  color: var(--color-blue-gray);
  position: absolute;
  top: var(--space-sm);
  right: var(--space-sm);
}

.board-note {
  display: block;
  border-left: 2px solid var(--color-orange);
  padding-left: var(--space-sm);
  margin-bottom: var(--space-sm);
  font-size: 13px;
  color: var(--color-blue-gray);
  line-height: 1.7;
}

.board-term {
  color: var(--color-orange-light);
  font-weight: 500;
}

/* ---------- 13. Tags ---------- */
.tag {
  display: inline-block;
  padding: 3px 10px;
  font-family: var(--font-body);
  font-size: 11px;
  letter-spacing: 0.08em;
  color: var(--color-silver);
  background: var(--color-blue-light);
  border: 1px solid var(--border-mid);
  text-transform: uppercase;
}

.tag-accent {
  background: var(--color-orange-light);
  border-color: var(--color-orange-light);
  color: var(--color-dark);
  font-weight: 600;
}

/* ---------- 14. Breadcrumbs ---------- */
.breadcrumbs {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  padding: var(--space-sm) 0;
  font-family: var(--font-body);
  font-size: 13px;
  border-bottom: 1px solid var(--border-faint);
  margin-bottom: var(--space-lg);
}

.breadcrumbs-link {
  color: var(--color-blue-gray);
  text-decoration: none;
}

.breadcrumbs-link:hover {
  color: var(--color-orange);
}

.breadcrumbs-sep {
  color: var(--color-blue-gray);
  opacity: 0.45;
}

.breadcrumbs-current {
  color: var(--color-white);
  font-weight: 500;
}

/* ---------- 15. Image Shell ---------- */
.image-shell {
  position: relative;
  display: block;
  width: 100%;
  aspect-ratio: 16 / 9;
  background: linear-gradient(135deg, var(--color-blue-light) 0%, var(--color-blue) 100%);
  border: 1px solid var(--color-blue-gray);
  overflow: hidden;
}

.image-shell[data-ratio="21-9"] { aspect-ratio: 21 / 9; }
.image-shell[data-ratio="4-3"] { aspect-ratio: 4 / 3; }
.image-shell[data-ratio="1-1"] { aspect-ratio: 1 / 1; }

.image-shell img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

.image-shell[data-label]::after {
  content: attr(data-label);
  position: absolute;
  left: 0;
  bottom: 0;
  padding: 4px 12px;
  font-family: var(--font-body);
  font-size: 10px;
  letter-spacing: 0.1em;
  color: var(--color-silver);
  background: rgba(11, 27, 43, 0.8);
  border-top: 1px solid var(--border-mid);
}

/* ---------- 16. Trace & Stripes ---------- */
.trace-guide {
  position: relative;
  padding-left: 22px;
}

.trace-guide::before {
  content: "";
  position: absolute;
  left: 4px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(180deg, var(--color-orange) 0%, var(--color-blue-gray) 60%, transparent 100%);
}

.stripes {
  background: repeating-linear-gradient(
    -45deg,
    rgba(255, 107, 44, 0.05) 0,
    rgba(255, 107, 44, 0.05) 1px,
    transparent 1px,
    transparent 10px
  );
}

/* ---------- 17. Reveal on Scroll ---------- */
[data-reveal] {
  opacity: 1;
  transform: none;
  transition: opacity var(--ease-medium), transform var(--ease-medium);
}

html.js [data-reveal]:not(.is-visible) {
  opacity: 0;
  transform: translateY(24px);
}

/* ---------- 18. Reduced Motion ---------- */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }

  html {
    scroll-behavior: auto !important;
  }

  html.js [data-reveal]:not(.is-visible) {
    opacity: 1;
    transform: none;
  }
}