:root {
  --bg: #0a0e12;
  --bg-elev: #0f1419;
  --panel: rgba(12, 20, 28, 0.72);
  --line: rgba(58, 196, 196, 0.28);
  --line-soft: rgba(168, 214, 230, 0.12);
  --ink: #f2f5f0;
  --muted: #8a9aa8;
  --cyan: #3ac4c4;
  --cyan-dim: #1f8f8f;
  --coral: #ff7a45;
  --amber: #e8a23a;
  --ok: #5dca8a;
  --danger: #e37a6a;
  --mono: "IBM Plex Mono", "JetBrains Mono", ui-monospace, monospace;
  --sans: "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", sans-serif;
  --display: "Bricolage Grotesque", "Syne", var(--sans);
  --max: 1080px;
  --radius: 14px;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: var(--sans);
  background: var(--bg);
  line-height: 1.55;
}

a { color: inherit; text-decoration: none; }
code, .mono { font-family: var(--mono); }

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--cyan);
  color: #041414;
  padding: 0.5rem 0.75rem;
  z-index: 999;
}
.skip-link:focus { left: 0.5rem; top: 0.5rem; }

/* faint particle field */
.atmosphere {
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(900px 500px at 15% -5%, rgba(58, 196, 196, 0.12), transparent 55%),
    radial-gradient(700px 420px at 90% 10%, rgba(255, 122, 69, 0.08), transparent 50%),
    linear-gradient(180deg, #070b0f 0%, #0a0e12 45%, #0b1116 100%);
  pointer-events: none;
}

.site-header {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1rem 1.25rem 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
  font-family: var(--display);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.1;
}
.brand span { font-size: 1.15rem; }
.brand small {
  font-family: var(--mono);
  font-size: 0.68rem;
  font-weight: 400;
  color: var(--cyan);
  letter-spacing: 0.04em;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
  color: var(--muted);
  font-size: 0.88rem;
  font-family: var(--mono);
}
.nav a:hover,
.nav a[aria-current="page"] { color: var(--ink); }

.pill {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--cyan);
}
.pill::before {
  content: "";
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--cyan);
  box-shadow: 0 0 8px var(--cyan);
}

.hero {
  max-width: var(--max);
  margin: 0 auto;
  padding: clamp(3.5rem, 12vh, 6.5rem) 1.25rem 2.5rem;
  text-align: center;
}

.hero h1 {
  margin: 0.7rem 0 0;
  font-family: var(--display);
  font-size: clamp(2.8rem, 8vw, 5.2rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  color: var(--coral);
  line-height: 1;
}

.hero-lead {
  max-width: 46rem;
  margin: 1.1rem auto 0;
  color: var(--ink);
  font-size: 1rem;
}
.hero-lead .en {
  display: block;
  margin-top: 0.45rem;
  color: var(--cyan);
  font-family: var(--mono);
  font-size: 0.82rem;
  line-height: 1.55;
}

.hero-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
  justify-content: center;
  margin-top: 1.6rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.7rem 1.1rem;
  border-radius: 999px;
  border: 1px solid transparent;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.15s ease, background 0.15s ease, border-color 0.15s ease;
}
.btn:hover { transform: translateY(-1px); }
.btn-primary {
  background: var(--cyan);
  color: #041414;
}
.btn-primary:hover { background: #5ad5d5; }
.btn-ghost {
  border-color: var(--line);
  background: transparent;
  color: var(--ink);
}
.btn-ghost:hover { border-color: var(--cyan); color: var(--cyan); }

/* terminal window */
.terminal {
  max-width: 720px;
  margin: 2rem auto 0;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: rgba(8, 14, 20, 0.85);
  overflow: hidden;
  text-align: left;
  box-shadow: 0 0 0 1px rgba(58, 196, 196, 0.05), 0 20px 60px rgba(0, 0, 0, 0.35);
}
.terminal-bar {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.65rem 0.85rem;
  border-bottom: 1px solid var(--line-soft);
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
}
.terminal-dot {
  width: 9px;
  height: 9px;
  border-radius: 50%;
}
.terminal-dot.r { background: #ff5f57; }
.terminal-dot.y { background: #febc2e; }
.terminal-dot.g { background: #28c840; }
.terminal-body {
  padding: 1rem 1.1rem 1.2rem;
  font-family: var(--mono);
  font-size: 0.86rem;
  line-height: 1.7;
}
.terminal-body .cmd { color: var(--muted); }
.terminal-body .name { color: var(--coral); }
.terminal-body .tag {
  display: inline-block;
  margin: 0 0.45rem;
  padding: 0.05rem 0.4rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--cyan);
  font-size: 0.7rem;
}
.terminal-body .phase { color: var(--ink); }
.terminal-cursor {
  display: inline-block;
  width: 0.55ch;
  height: 1.1em;
  background: var(--cyan);
  vertical-align: text-bottom;
  animation: blink 1s step-end infinite;
}
@keyframes blink { 50% { opacity: 0; } }

.section {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1.5rem 1.25rem 3.5rem;
}

.section-head {
  margin-bottom: 1.25rem;
}
.section-head h2 {
  margin: 0.4rem 0 0;
  font-family: var(--display);
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  letter-spacing: -0.03em;
}
.section-head p {
  margin: 0.55rem 0 0;
  color: var(--muted);
  max-width: 40rem;
}

.module-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.85rem;
}
@media (min-width: 760px) {
  .module-grid { grid-template-columns: 1fr 1fr; }
}

.module {
  display: block;
  padding: 1.15rem 1.2rem 1.2rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  backdrop-filter: blur(8px);
  transition: border-color 0.2s ease, transform 0.2s ease, box-shadow 0.2s ease;
}
.module:hover {
  border-color: rgba(58, 196, 196, 0.55);
  transform: translateY(-2px);
  box-shadow: 0 0 24px rgba(58, 196, 196, 0.08);
}

.module-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
}
.module-idx {
  font-family: var(--mono);
  color: var(--cyan);
  font-size: 0.85rem;
}
.module-tag {
  font-family: var(--mono);
  font-size: 0.7rem;
  padding: 0.15rem 0.5rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--cyan);
}
.module h3 {
  margin: 0;
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}
.module .en {
  margin: 0.45rem 0 0;
  color: var(--muted);
  font-family: var(--mono);
  font-size: 0.78rem;
  line-height: 1.5;
}
.module .zh {
  margin: 0.45rem 0 0;
  color: var(--ink);
  font-size: 0.92rem;
}
.module-meta {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  margin-top: 0.9rem;
}
.module-meta .ver {
  font-family: var(--mono);
  font-size: 0.75rem;
  color: var(--muted);
}
.bar {
  flex: 1;
  height: 3px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.08);
  overflow: hidden;
}
.bar i {
  display: block;
  width: var(--p);
  height: 100%;
  background: linear-gradient(90deg, var(--cyan-dim), var(--cyan));
}
.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.75rem;
}
.tags span {
  font-size: 0.72rem;
  font-family: var(--mono);
  padding: 0.18rem 0.5rem;
  border-radius: 999px;
  border: 1px solid var(--line-soft);
  color: var(--muted);
}
.tags .ok {
  color: var(--ok);
  border-color: rgba(93, 202, 138, 0.35);
}
.tags .dev {
  color: var(--amber);
  border-color: rgba(232, 162, 58, 0.35);
}

.site-footer {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1.25rem 1.25rem 2.5rem;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.75rem;
  color: var(--muted);
  font-size: 0.82rem;
  font-family: var(--mono);
  border-top: 1px solid var(--line-soft);
}
.site-footer a { color: var(--cyan); }

/* calculator / older pages reuse */
.page-intro { margin-bottom: 1.5rem; }
.page-intro h1 {
  margin: 0.35rem 0 0;
  font-family: var(--display);
  font-size: clamp(1.8rem, 4vw, 2.6rem);
  color: var(--coral);
  letter-spacing: -0.03em;
}
.eyebrow {
  margin: 0;
  font-family: var(--mono);
  font-size: 0.8rem;
  color: var(--cyan);
}
.page-intro p { color: var(--muted); margin: 0.55rem 0 0; max-width: 40rem; }

.products-main,
.calc-main,
.docs-main,
.workbench {
  max-width: var(--max);
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

.product-grid { display: grid; grid-template-columns: 1fr; gap: 0.85rem; }
@media (min-width: 760px) {
  .product-grid { grid-template-columns: 1fr 1fr; }
}
.product { /* alias to module for old markup */ }

.panel {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  padding: 1.15rem;
}
.panel label {
  display: grid;
  gap: 0.3rem;
  margin-bottom: 0.85rem;
  color: var(--muted);
  font-size: 0.88rem;
  font-family: var(--mono);
}
.panel input,
.panel select,
.panel textarea {
  width: 100%;
  padding: 0.65rem 0.75rem;
  border-radius: 8px;
  border: 1px solid var(--line-soft);
  background: rgba(5, 10, 16, 0.75);
  color: var(--ink);
  font: inherit;
}
.panel input:focus,
.panel select:focus {
  outline: 2px solid rgba(58, 196, 196, 0.3);
  border-color: var(--cyan);
}
.row { display: grid; grid-template-columns: 1fr 1fr; gap: 0.7rem; }
.hint { margin: 0.75rem 0 0; color: var(--muted); font-size: 0.85rem; }
.hint.ok { color: var(--ok); }
.hint.error { color: var(--danger); }
pre {
  margin: 0;
  padding: 0.85rem;
  border-radius: 8px;
  background: rgba(5, 10, 16, 0.75);
  border: 1px solid var(--line-soft);
  overflow: auto;
  font-family: var(--mono);
  font-size: 0.84rem;
  white-space: pre-wrap;
  word-break: break-word;
}
pre.is-error { color: var(--danger); }

/* calc extras kept */
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}
.calc-layout { display: grid; gap: 1rem; }
@media (min-width: 900px) {
  .calc-layout { grid-template-columns: 1.15fr 0.85fr; align-items: start; }
}
.calc-tabs { display: flex; gap: 0.4rem; flex-wrap: wrap; margin-bottom: 1rem; }
.calc-tab {
  appearance: none; border: 1px solid var(--line); background: transparent;
  color: var(--muted); border-radius: 999px; padding: 0.4rem 0.85rem;
  font: inherit; font-size: 0.85rem; cursor: pointer; font-family: var(--mono);
}
.calc-tab.is-active { color: #041414; background: var(--cyan); border-color: transparent; }
.calc-display {
  width: 100%; margin-bottom: 0.85rem; padding: 0.9rem 1rem;
  border-radius: 10px; border: 1px solid var(--line-soft);
  background: rgba(5, 10, 16, 0.75); color: var(--ink);
  font-family: var(--mono); font-size: 1.1rem;
}
.calc-keys {
  display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0.4rem;
}
.calc-keys button {
  appearance: none; border: 1px solid var(--line-soft);
  background: rgba(10, 18, 26, 0.9); color: var(--ink);
  border-radius: 10px; min-height: 2.6rem; font: inherit;
  font-family: var(--mono); cursor: pointer;
}
.calc-keys .key-eq {
  grid-column: span 3; background: var(--cyan); color: #041414; border-color: transparent; font-weight: 700;
}
.history { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.5rem; }
.history li {
  display: grid; gap: 0.1rem; padding: 0.65rem 0.75rem;
  border: 1px solid var(--line-soft); border-radius: 8px; background: rgba(5, 10, 16, 0.5);
}
.history strong { font-family: var(--mono); color: var(--cyan); }
.history span, .history em { color: var(--muted); font-size: 0.82rem; font-style: normal; }
.result-panel .subhead { margin-top: 1.2rem; }
.phys-fields { display: grid; gap: 0.15rem; }

.cost-table { width: 100%; border-collapse: collapse; margin: 1rem 0; font-size: 0.92rem; }
.cost-table th, .cost-table td {
  border: 1px solid var(--line-soft); padding: 0.6rem 0.7rem; text-align: left;
}
.cost-table th { background: rgba(14, 28, 42, 0.9); }

.inline-links {
  display: flex; flex-wrap: wrap; gap: 1.1rem; margin-top: 1.1rem;
}
.inline-links a { color: var(--cyan); font-family: var(--mono); font-size: 0.9rem; }
.steps { list-style: none; margin: 1.5rem 0 0; padding: 0; display: grid; gap: 0.25rem; }
.steps li {
  display: grid; grid-template-columns: auto 1fr; gap: 1rem;
  padding: 1rem 0; border-top: 1px solid var(--line-soft);
}
.steps h3 { margin: 0 0 0.3rem; font-size: 1.02rem; }
.steps p { margin: 0; color: var(--muted); }
.step-num { font-family: var(--mono); color: var(--cyan); font-size: 0.9rem; padding-top: 0.15rem; }