/* ============================================================
   北凑 beicou.com — main.css
   设计语言：深色 / 终端极简 / 表格优先 / OpenAI 文档风
   v1.3 修真：去掉"拼团"叙事 UI，留下价格表 + 代码块 + 步骤
   ============================================================ */

:root {
  --bg: #0a0a0a;
  --bg-alt: #111113;
  --bg-elev: #16161a;
  --border: #232328;
  --border-soft: #1c1c20;
  --text: #f4f4f5;
  --text-mid: #a1a1aa;
  --text-dim: #71717a;
  --accent: #7dd3fc;
  --accent-2: #38bdf8;
  --accent-glow: rgba(125, 211, 252, 0.18);
  --warn: #facc15;
  --danger: #f87171;
  --good: #4ade80;

  --radius: 10px;
  --radius-sm: 6px;
  --radius-lg: 14px;
  --maxw: 1180px;
  --maxw-narrow: 760px;

  --font-sans: -apple-system, BlinkMacSystemFont, "PingFang SC",
               "Hiragino Sans GB", "Microsoft YaHei", "Segoe UI", Roboto, sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", Menlo, Consolas, "Roboto Mono", monospace;

  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

/* ============== RESET ============== */
*, *::before, *::after { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  text-rendering: optimizeLegibility;
}
img, svg { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; border: none; background: none; color: inherit; }
input, textarea, select { font-family: inherit; }
code, pre { font-family: var(--font-mono); }

::selection { background: var(--accent); color: #000; }

/* ============== LAYOUT ============== */
.container {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 28px;
}
.container.narrow { max-width: var(--maxw-narrow); }

/* ============== HEADER ============== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(10, 10, 10, 0.78);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--border-soft);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  gap: 24px;
}
.logo {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  letter-spacing: 0.02em;
}
.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  border-radius: 6px;
  background: var(--accent);
  color: #000;
  font-weight: 800;
  font-family: var(--font-mono);
  font-size: 14px;
}
.logo-text { font-size: 14px; color: var(--text); }

.nav {
  display: flex;
  gap: 28px;
  font-size: 14px;
  color: var(--text-mid);
  align-items: center;
}
.nav a { transition: color 0.2s var(--ease); }
.nav a:hover { color: var(--text); }

@media (max-width: 720px) {
  .nav { display: none; }
}

/* ============== BUTTONS ============== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 20px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.01em;
  transition: transform 0.18s var(--ease), background 0.2s var(--ease), color 0.2s var(--ease), border-color 0.2s var(--ease);
  border: 1px solid transparent;
  white-space: nowrap;
}
.btn-sm { padding: 8px 14px; font-size: 13px; }
.btn-lg { padding: 16px 28px; font-size: 15px; }

.btn-primary {
  background: var(--accent);
  color: #001018;
}
.btn-primary:hover {
  background: #93dcfd;
  transform: translateY(-1px);
}
.btn-primary:active { transform: translateY(0); }

.btn-ghost {
  background: transparent;
  color: var(--text);
  border-color: var(--border);
}
.btn-ghost:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.btn-link {
  background: transparent;
  color: var(--text-mid);
  padding: 12px 4px;
}
.btn-link:hover { color: var(--accent); }

/* ============== HERO ============== */
.hero {
  padding: 96px 0 80px;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  top: -200px;
  left: 50%;
  transform: translateX(-50%);
  width: 900px;
  height: 900px;
  background: radial-gradient(circle, var(--accent-glow) 0%, transparent 60%);
  pointer-events: none;
  z-index: 0;
}
.hero > .container { position: relative; z-index: 1; }

.eyebrow {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--text-dim);
  margin-bottom: 24px;
}

.hero-title {
  font-size: clamp(44px, 6.4vw, 80px);
  line-height: 1.05;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin: 0 0 28px;
}
.hero-title .accent {
  background: linear-gradient(120deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero-sub {
  max-width: 640px;
  font-size: 18px;
  line-height: 1.85;
  color: var(--text-mid);
  margin: 0 0 36px;
  letter-spacing: 0.005em;
}
.hero-sub strong { color: var(--text); font-weight: 600; }

.hero-cta {
  display: flex;
  gap: 16px;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 48px;
}

/* ============== HERO CODE BLOCK ============== */
.hero-code {
  margin-bottom: 56px;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--bg-elev);
  overflow: hidden;
  position: relative;
}
.code-tabs {
  display: flex;
  gap: 4px;
  padding: 8px 12px 0;
  background: var(--bg);
  border-bottom: 1px solid var(--border-soft);
}
.code-tab {
  font-size: 12px;
  font-family: var(--font-mono);
  color: var(--text-dim);
  padding: 8px 14px;
  border-radius: 6px 6px 0 0;
  cursor: default;
}
.code-tab.is-active {
  color: var(--accent);
  background: var(--bg-elev);
  border: 1px solid var(--border-soft);
  border-bottom-color: var(--bg-elev);
  margin-bottom: -1px;
}
.code-block {
  margin: 0;
  padding: 22px 26px 26px;
  font-size: 13.5px;
  line-height: 1.7;
  color: var(--text);
  overflow-x: auto;
  white-space: pre;
}
.code-block code { display: block; }
.code-block .c { color: var(--text-dim); font-style: italic; }
.code-block .k { color: #c084fc; }
.code-block .s { color: #86efac; }
.code-block .n { color: #fbbf24; }
.code-block .m { color: var(--accent); }

@media (max-width: 720px) {
  .hero { padding: 64px 0 48px; }
  .code-block { font-size: 12px; padding: 16px 18px; }
}

/* ============== HERO STATS ============== */
.hero-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 28px;
  border-top: 1px solid var(--border-soft);
  padding-top: 36px;
}
.stat {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.stat-num {
  font-family: var(--font-mono);
  font-size: 28px;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
}
.stat-label {
  font-size: 13px;
  color: var(--text-dim);
}
@media (max-width: 720px) {
  .hero-stats { grid-template-columns: repeat(2, 1fr); gap: 20px; }
}

/* ============== SECTION ============== */
.section {
  padding: 96px 0;
  border-top: 1px solid var(--border-soft);
}
.section-alt { background: var(--bg-alt); }

.section-title {
  font-size: clamp(32px, 4.2vw, 52px);
  line-height: 1.15;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin: 0 0 16px;
}
.section-lead {
  font-size: 17px;
  color: var(--text-mid);
  max-width: 680px;
  margin: 0 0 56px;
}
.section-lead code,
.section-foot code {
  font-family: var(--font-mono);
  font-size: 13px;
  background: var(--border-soft);
  padding: 1px 7px;
  border-radius: 4px;
  color: var(--accent);
}
.section-foot {
  margin-top: 28px;
  color: var(--text-dim);
  font-size: 14px;
  line-height: 1.7;
  max-width: 720px;
}
.section-foot strong { color: var(--text); font-weight: 600; }

@media (max-width: 720px) {
  .section { padding: 64px 0; }
}

/* ============== MODEL TABLE ============== */
.model-table-wrap {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--bg-elev);
}
.model-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
}
.model-table th,
.model-table td {
  padding: 16px 20px;
  text-align: left;
  border-bottom: 1px solid var(--border-soft);
  vertical-align: top;
}
.model-table thead th {
  background: var(--bg-alt);
  font-family: var(--font-mono);
  font-size: 11px;
  font-weight: 600;
  color: var(--text-dim);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  line-height: 1.5;
}
.model-table .th-sub {
  font-size: 10px;
  font-weight: 500;
  color: var(--text-dim);
  text-transform: none;
  letter-spacing: 0.02em;
  margin-top: 2px;
  display: inline-block;
}
.model-table tbody tr:last-child td { border-bottom: none; }
.model-table tbody tr:hover { background: rgba(125, 211, 252, 0.025); }
.model-table code.m {
  display: inline-block;
  font-size: 13px;
  color: var(--accent);
  font-weight: 600;
  background: rgba(125, 211, 252, 0.08);
  padding: 2px 8px;
  border-radius: 4px;
  border: 1px solid rgba(125, 211, 252, 0.18);
}
.m-tag {
  font-size: 11px;
  color: var(--text-dim);
  margin-top: 4px;
  font-family: var(--font-mono);
  letter-spacing: 0.02em;
}
.t-price {
  font-family: var(--font-mono);
  color: var(--text);
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.t-off {
  font-family: var(--font-mono);
  color: var(--text-dim);
  text-decoration: line-through;
  font-size: 12.5px;
  font-variant-numeric: tabular-nums;
}
.badge-firstweek {
  display: inline-block;
  margin-left: 6px;
  padding: 1px 7px;
  font-size: 10px;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--warn);
  background: rgba(250, 204, 21, 0.1);
  border: 1px solid rgba(250, 204, 21, 0.4);
  border-radius: 999px;
  letter-spacing: 0.04em;
  vertical-align: middle;
  text-transform: uppercase;
  text-decoration: none;
}

@media (max-width: 860px) {
  .model-table { font-size: 12.5px; }
  .model-table th, .model-table td { padding: 12px 14px; }
  .model-table .th-sub { display: block; }
}

/* ============== STEPS ============== */
.step-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  counter-reset: step;
}
@media (max-width: 860px) {
  .step-grid { grid-template-columns: 1fr; }
}
.step {
  padding: 32px 28px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-elev);
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.step-num {
  font-family: var(--font-mono);
  font-size: 36px;
  font-weight: 800;
  color: var(--accent);
  letter-spacing: -0.02em;
  font-variant-numeric: tabular-nums;
  line-height: 1;
}
.step h3 {
  font-size: 20px;
  margin: 0;
  font-weight: 700;
}
.step p {
  font-size: 14px;
  color: var(--text-mid);
  margin: 0;
  line-height: 1.6;
}
.step p a {
  color: var(--accent);
  border-bottom: 1px dashed var(--accent);
}
.step code {
  font-family: var(--font-mono);
  font-size: 12.5px;
  background: var(--border-soft);
  padding: 1px 6px;
  border-radius: 4px;
  color: var(--accent);
}

/* ============== CODE MINI (复制按钮) ============== */
.code-mini {
  margin-top: 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  padding: 10px 14px;
  background: var(--bg);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius-sm);
  font-size: 12.5px;
}
.code-mini code {
  font-family: var(--font-mono);
  color: var(--accent);
  font-size: 12.5px;
  overflow-x: auto;
  white-space: nowrap;
  flex: 1;
  min-width: 0;
}
.copy-btn {
  flex: 0 0 auto;
  padding: 4px 10px;
  font-size: 11px;
  font-family: var(--font-mono);
  font-weight: 600;
  color: var(--text-mid);
  background: var(--border-soft);
  border: 1px solid var(--border);
  border-radius: 4px;
  letter-spacing: 0.04em;
  transition: all 0.15s var(--ease);
  cursor: pointer;
}
.copy-btn:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: rgba(125, 211, 252, 0.06);
}
.copy-btn.is-copied {
  color: var(--good);
  border-color: var(--good);
  background: rgba(74, 222, 128, 0.08);
}

/* ============== COMPAT PILLS ============== */
.compat {
  margin-top: 56px;
  padding-top: 32px;
  border-top: 1px solid var(--border-soft);
}
.compat h3 {
  font-size: 14px;
  color: var(--text-dim);
  font-family: var(--font-mono);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin: 0 0 16px;
  font-weight: 600;
}
.compat-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.compat-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 14px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: 13px;
  color: var(--text);
  font-weight: 500;
}
.compat-sub {
  font-size: 11px;
  color: var(--text-dim);
  font-family: var(--font-mono);
  padding-left: 6px;
  border-left: 1px solid var(--border);
  margin-left: 2px;
}

/* ============== WHY GRID ============== */
.why-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
@media (max-width: 860px) {
  .why-grid { grid-template-columns: 1fr; }
}
.why-item {
  padding: 28px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg-elev);
}
.why-num {
  font-family: var(--font-mono);
  color: var(--accent);
  font-size: 13px;
  margin-bottom: 16px;
  letter-spacing: 0.1em;
}
.why-item h3 {
  font-size: 20px;
  margin: 0 0 12px;
  font-weight: 700;
}
.why-item p {
  font-size: 14px;
  color: var(--text-mid);
  line-height: 1.6;
  margin: 0;
}

/* ============== CALCULATOR (余额能撑多久) ============== */
.calc {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--bg-elev);
  padding: 36px;
  display: flex;
  flex-direction: column;
  gap: 28px;
  position: relative;
  overflow: hidden;
}
.calc::before {
  content: "";
  position: absolute;
  top: -120px;
  right: -120px;
  width: 320px;
  height: 320px;
  background: radial-gradient(circle, var(--accent-glow) 0%, transparent 60%);
  pointer-events: none;
}
.calc-row {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
  align-items: end;
}
.calc-label { display: flex; flex-direction: column; gap: 6px; }
.calc-title {
  font-size: 14px;
  font-weight: 700;
  color: var(--text);
}
.calc-hint {
  font-size: 12.5px;
  color: var(--text-dim);
  line-height: 1.5;
}
.calc-input-wrap {
  position: relative;
  display: flex;
  align-items: center;
}
.calc-input-wrap input {
  width: 100%;
  padding: 14px 70px 14px 16px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 24px;
  font-weight: 700;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.01em;
  transition: border-color 0.2s var(--ease);
}
.calc-input-wrap input:focus {
  outline: none;
  border-color: var(--accent);
}
.calc-unit {
  position: absolute;
  right: 16px;
  font-size: 13px;
  color: var(--text-dim);
  font-family: var(--font-mono);
  pointer-events: none;
}

.calc-pick {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.calc-pick-label {
  font-size: 13px;
  color: var(--text-dim);
  font-family: var(--font-mono);
  letter-spacing: 0.06em;
  text-transform: uppercase;
}
.calc-pick-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}
.pick {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 4px;
  padding: 12px 14px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 13px;
  font-weight: 600;
  text-align: left;
  transition: border-color 0.2s var(--ease), background 0.2s var(--ease);
}
.pick:hover { border-color: var(--text-mid); }
.pick.is-active {
  border-color: var(--accent);
  background: rgba(125, 211, 252, 0.06);
  color: var(--text);
}
.pick-save {
  font-size: 11px;
  color: var(--good);
  font-family: var(--font-mono);
  font-weight: 700;
  letter-spacing: 0.02em;
}

.calc-result {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  padding: 28px 24px;
  background: var(--bg);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
}
.calc-col {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 0 8px;
  border-right: 1px solid var(--border-soft);
}
.calc-col:last-child { border-right: none; }
.calc-col-label {
  font-size: 12px;
  color: var(--text-dim);
  font-family: var(--font-mono);
  letter-spacing: 0.06em;
  text-transform: uppercase;
}
.calc-col-num {
  font-size: 28px;
  font-weight: 800;
  color: var(--text);
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.02em;
  line-height: 1.1;
}
.calc-col-mid .calc-col-num { color: var(--accent); }
.calc-col-win .calc-col-num { color: var(--good); }
.calc-col-foot {
  font-size: 12px;
  color: var(--text-dim);
  line-height: 1.4;
}

@media (max-width: 860px) {
  .calc { padding: 24px; }
  .calc-row { grid-template-columns: 1fr; gap: 16px; }
  .calc-pick-grid { grid-template-columns: 1fr; }
  .calc-result { grid-template-columns: 1fr; gap: 16px; padding: 20px 16px; }
  .calc-col { border-right: none; border-bottom: 1px solid var(--border-soft); padding-bottom: 16px; }
  .calc-col:last-child { border-bottom: none; padding-bottom: 0; }
}

/* ============== FAQ ============== */
.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 12px;
  background: var(--bg-elev);
  overflow: hidden;
  transition: border-color 0.2s var(--ease);
}
.faq-item:hover { border-color: var(--text-dim); }
.faq-item[open] { border-color: var(--accent); }
.faq-item summary {
  padding: 18px 22px;
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  user-select: none;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: "+";
  font-family: var(--font-mono);
  font-size: 18px;
  color: var(--text-dim);
  transition: transform 0.2s var(--ease), color 0.2s var(--ease);
}
.faq-item[open] summary::after {
  content: "−";
  color: var(--accent);
}
.faq-item > *:not(summary) {
  padding: 0 22px 20px;
  margin: 0;
  font-size: 14.5px;
  line-height: 1.75;
  color: var(--text-mid);
}
.faq-item p { margin: 0; }
.faq-item code {
  font-family: var(--font-mono);
  font-size: 12.5px;
  background: var(--border-soft);
  padding: 1px 6px;
  border-radius: 4px;
  color: var(--accent);
}
.faq-item a {
  color: var(--accent);
  border-bottom: 1px dashed var(--accent);
}

/* ============== FINAL CTA ============== */
.final-cta { text-align: left; }
.final-cta .section-lead { margin-bottom: 36px; }
.final-cta-row {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  align-items: center;
}

/* ============== GSAP INITIAL STATES ============== */
/* 这些元素在 GSAP 加载前都默认可见（no-JS fallback）
   GSAP 加载后会立即用 from() 设 opacity:0 然后播动画
   父元素用 data-split-lines 的不动，子元素由 GSAP 即时控制 */
/* prefers-reduced-motion 时强制可见 */
@media (prefers-reduced-motion: reduce) {
  .gsap-ready [data-fade],
  .gsap-ready [data-reveal] > .container > *,
  .gsap-ready [data-stagger-row] {
    opacity: 1 !important;
    transform: none !important;
  }
}

/* ============== FOOTER ============== */
.site-footer {
  background: var(--bg-alt);
  border-top: 1px solid var(--border-soft);
  padding: 56px 0 24px;
  margin-top: 0;
}
.footer-inner {
  display: grid;
  grid-template-columns: 1.4fr 1fr;
  gap: 56px;
  margin-bottom: 36px;
}
.footer-brand > span {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  margin-bottom: 10px;
}
.footer-tag {
  margin: 6px 0 0;
  font-size: 14px;
  color: var(--text-mid);
}
.footer-compliance {
  margin: 10px 0 0;
  font-size: 11.5px;
  color: var(--text-dim);
  font-family: var(--font-mono);
  letter-spacing: 0.04em;
}
.footer-cols {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 36px;
}
.footer-cols h4 {
  font-size: 12px;
  font-family: var(--font-mono);
  color: var(--text-dim);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin: 0 0 14px;
  font-weight: 600;
}
.footer-cols a {
  display: block;
  font-size: 14px;
  color: var(--text-mid);
  padding: 4px 0;
  transition: color 0.2s var(--ease);
}
.footer-cols a:hover { color: var(--accent); }
.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 24px;
  border-top: 1px solid var(--border-soft);
  font-size: 12.5px;
  color: var(--text-dim);
}
.footer-bottom a { color: var(--text-mid); }
.footer-bottom a:hover { color: var(--accent); }

@media (max-width: 720px) {
  .footer-inner { grid-template-columns: 1fr; gap: 32px; }
  .footer-cols { grid-template-columns: 1fr 1fr; gap: 24px; }
  .footer-bottom { flex-direction: column; gap: 8px; align-items: flex-start; }
}