:root {
  --ink: #152238;
  --ink-soft: #3d4a5c;
  --ink-muted: #6b7789;
  --line: #d7e0ea;
  --surface: #f3f6f9;
  --accent: #2f6f7c;
  --accent-deep: #1f4f59;
  --warn-bg: #f7f1e6;
  --warn: #7a5b28;
  --font-display: "Fraunces", "Noto Serif SC", Georgia, serif;
  --font-body: "Manrope", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: var(--font-body);
  color: var(--ink);
  background:
    radial-gradient(ellipse 70% 40% at 10% 0%, rgba(47, 111, 124, 0.12), transparent 55%),
    linear-gradient(180deg, #f7fafc 0%, var(--surface) 100%);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; }

.brief-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.1rem 1.5rem;
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 10;
}

.brand {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1.15rem;
  text-decoration: none;
}

.brief-top nav {
  display: flex;
  gap: 1rem;
  font-size: 0.92rem;
}

.brief-top nav a {
  text-decoration: none;
  color: var(--ink-soft);
}

.brief-top nav a:hover { color: var(--accent); }

.brief-main {
  width: min(760px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 2.5rem 0 4rem;
}

.kicker {
  font-family: var(--font-display);
  letter-spacing: 0.12em;
  color: var(--accent);
  font-size: 0.85rem;
  margin-bottom: 0.6rem;
}

.brief-main > h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 5vw, 2.75rem);
  line-height: 1.2;
  margin-bottom: 0.75rem;
}

.lead {
  font-size: 1.08rem;
  color: var(--ink-soft);
  margin-bottom: 2rem;
  max-width: 42rem;
}

.block {
  padding: 1.4rem 0;
  border-top: 1px solid var(--line);
}

.block h2 {
  font-family: var(--font-display);
  font-size: 1.35rem;
  margin-bottom: 0.7rem;
}

.block h3 {
  font-family: var(--font-body);
  font-size: 1.05rem;
  font-weight: 700;
  margin: 1rem 0 0.45rem;
}

.block p { margin-bottom: 0.7rem; color: var(--ink-soft); }

.block ul,
.block ol {
  padding-left: 1.2rem;
  margin-bottom: 0.9rem;
  color: var(--ink);
}

.block li { margin-bottom: 0.4rem; }

.note {
  background: var(--warn-bg);
  color: var(--warn);
  padding: 0.8rem 1rem;
  border-radius: 10px;
  font-size: 0.95rem;
}

.accept {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 0.85rem 1rem;
  color: var(--ink) !important;
}

.highlight {
  background: rgba(255, 255, 255, 0.7);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 1.25rem 1.2rem;
  margin: 1rem 0;
}

.subhead {
  font-family: var(--font-display);
  font-size: 1.05rem;
  margin: 1.1rem 0 0.55rem;
  color: var(--ink);
}

.key-box {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
  background: #12202b;
  color: #e8f3f5;
  border-radius: 12px;
  padding: 0.9rem 1rem;
  margin: 0.6rem 0 0.9rem;
}

.key-box code {
  font-family: ui-monospace, "Cascadia Code", Consolas, monospace;
  font-size: 0.92rem;
  word-break: break-all;
  flex: 1;
  min-width: 12rem;
}

.copy-btn {
  border: 0;
  border-radius: 999px;
  background: var(--accent);
  color: #fff;
  font: inherit;
  font-weight: 650;
  font-size: 0.88rem;
  padding: 0.45rem 0.9rem;
  cursor: pointer;
}

.copy-btn:hover { background: var(--accent-deep); }

.env-sample,
.code-sample {
  background: #f8fafc;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 0.9rem 1rem;
  overflow-x: auto;
  font-family: ui-monospace, "Cascadia Code", Consolas, monospace;
  font-size: 0.82rem;
  line-height: 1.55;
  color: var(--ink);
  margin: 0.5rem 0 0.9rem;
  white-space: pre-wrap;
}

.hint-panel {
  margin-top: 1rem;
  border: 1px dashed #9eb8c2;
  border-radius: 14px;
  background: #eef6f7;
  overflow: hidden;
}

.hint-panel > summary {
  cursor: pointer;
  list-style: none;
  padding: 0.95rem 1.1rem;
  font-weight: 650;
  color: var(--accent-deep);
  user-select: none;
}

.hint-panel > summary::-webkit-details-marker { display: none; }

.hint-panel > summary::before {
  content: "▸ ";
  color: var(--accent);
}

.hint-panel[open] > summary::before { content: "▾ "; }

.hint-body {
  padding: 0 1.1rem 1.1rem;
  border-top: 1px solid #d5e4e8;
}

.hint-body p {
  margin: 0.85rem 0 0.45rem;
  color: var(--ink-soft);
}

.hint-body ul {
  margin-bottom: 0.4rem;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 0.75rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  padding: 0.7rem 1.15rem;
  border-radius: 999px;
  font-weight: 650;
  font-size: 0.95rem;
}

.btn.primary {
  background: var(--accent);
  color: #fff;
}

.btn.primary:hover { background: var(--accent-deep); }

.btn.ghost {
  border: 1px solid var(--line);
  background: #fff;
  color: var(--ink-soft);
}

.brief-foot {
  text-align: center;
  padding: 1.5rem;
  color: var(--ink-muted);
  font-size: 0.82rem;
  border-top: 1px solid var(--line);
}

@media (max-width: 640px) {
  .brief-top nav { display: none; }
}