:root {
  --bg: #fcfcfa;
  --fg: #1a2028;
  --muted: #5b6572;
  --card: #ffffff;
  --line: #e4e6e9;
  --accent: #0b6e6e;
  --accent-soft: #e3f1f0;
  --code-bg: #f2f3f4;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12151a;
    --fg: #e8eaed;
    --muted: #9aa4b0;
    --card: #191d24;
    --line: #2a2f38;
    --accent: #4fc3bd;
    --accent-soft: #16302f;
    --code-bg: #1f242c;
  }
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
/* bilingual: paired .en/.zh elements, html[data-lang] decides visibility */
html[data-lang="zh"] .en { display: none !important; }
html:not([data-lang="zh"]) .zh { display: none !important; }
#langToggle {
  cursor: pointer; border: 1px solid var(--line); background: var(--card); color: var(--muted);
  border-radius: 999px; padding: 4px 14px; font-size: .85rem; font-weight: 600;
  margin-left: 22px; vertical-align: baseline;
}
#langToggle:hover { color: var(--accent); border-color: var(--accent); }

/* marketplace mode: utm_source=upwork/fiverr hides direct contact (platform policy);
   .platform links (Upwork profile, GitHub) stay visible in all modes */
html[data-nocontact] .direct { display: none !important; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial,
    "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.65;
  font-size: 17px;
}
.wrap { max-width: 860px; margin: 0 auto; padding: 0 24px; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* header */
header.site {
  padding: 20px 0;
  border-bottom: 1px solid var(--line);
}
header.site .wrap { display: flex; justify-content: space-between; align-items: baseline; }
.brand { font-weight: 700; font-size: 1.1rem; color: var(--fg); letter-spacing: .01em; }
nav a { margin-left: 22px; color: var(--muted); font-size: .95rem; }
nav a:hover { color: var(--accent); text-decoration: none; }

/* hero */
.hero { padding: 84px 0 64px; }
.hero h1 { font-size: 2.6rem; line-height: 1.15; letter-spacing: -.02em; margin-bottom: 18px; }
.hero h1 em { font-style: normal; color: var(--accent); }
.hero p.sub { color: var(--muted); font-size: 1.15rem; max-width: 640px; }
.hero .cta { margin-top: 30px; }
.cta a.btn {
  display: inline-block; background: var(--accent); color: #fff;
  padding: 11px 22px; border-radius: 8px; font-weight: 600; font-size: .98rem;
}
.cta a.btn:hover { opacity: .9; text-decoration: none; }
.cta a.ghost { margin-left: 16px; color: var(--muted); font-size: .98rem; }

/* sections */
section { padding: 56px 0; border-top: 1px solid var(--line); }
h2.sec { font-size: 1.5rem; margin-bottom: 8px; letter-spacing: -.01em; }
p.sec-sub { color: var(--muted); margin-bottom: 34px; max-width: 620px; }

/* case cards */
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 20px; }
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px;
  overflow: hidden; display: flex; flex-direction: column;
  transition: transform .15s ease, box-shadow .15s ease;
}
.card:hover { transform: translateY(-2px); box-shadow: 0 6px 24px rgba(0,0,0,.08); }
.card a.body { color: var(--fg); padding: 20px; display: block; flex: 1; }
.card a.body:hover { text-decoration: none; }
.card .thumb { aspect-ratio: 16/9; background: var(--accent-soft); overflow: hidden; display: flex; align-items: center; justify-content: center; }
.card .thumb img { width: 100%; height: 100%; object-fit: cover; }
.card .thumb svg { width: 100%; height: 100%; }
.card h3 { font-size: 1.08rem; margin-bottom: 8px; }
.card p { color: var(--muted); font-size: .93rem; }
.card .stat { color: var(--accent); font-weight: 700; font-size: .85rem; text-transform: uppercase; letter-spacing: .05em; margin-bottom: 6px; }

/* how i work */
.how { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); gap: 20px; }
.how div {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 20px;
}
.how h3 { font-size: 1rem; margin-bottom: 8px; }
.how h3 .n { color: var(--accent); font-family: ui-monospace, monospace; margin-right: 8px; }
.how p { color: var(--muted); font-size: .92rem; }

/* contact */
.contact p { max-width: 620px; }
.contact .mail { font-size: 1.2rem; font-weight: 600; }

/* footer */
footer { border-top: 1px solid var(--line); padding: 28px 0 48px; color: var(--muted); font-size: .88rem; }

/* case study pages */
article.case { padding: 56px 0 24px; }
article.case h1 { font-size: 2rem; line-height: 1.2; letter-spacing: -.02em; margin-bottom: 10px; }
article.case p.lede { color: var(--muted); font-size: 1.1rem; margin-bottom: 8px; }
.tags { margin: 18px 0 8px; }
.tags span {
  display: inline-block; background: var(--accent-soft); color: var(--accent);
  border-radius: 6px; padding: 3px 10px; font-size: .8rem; font-weight: 600;
  margin: 0 8px 8px 0;
}
article.case h2 { font-size: 1.3rem; margin: 40px 0 12px; }
article.case p, article.case li { color: var(--fg); }
article.case ul { padding-left: 22px; margin: 12px 0; }
article.case li { margin-bottom: 8px; }
article.case .muted { color: var(--muted); }
figure { margin: 26px 0; }
figure img { max-width: 100%; border-radius: 10px; border: 1px solid var(--line); }
figure figcaption { color: var(--muted); font-size: .87rem; margin-top: 8px; }
.compare { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
@media (max-width: 640px) { .compare { grid-template-columns: 1fr; } }
.proof {
  background: var(--card); border: 1px solid var(--line); border-left: 4px solid var(--accent);
  border-radius: 10px; padding: 18px 20px; margin: 26px 0;
}
.proof strong { color: var(--accent); }
code { background: var(--code-bg); border-radius: 5px; padding: 2px 6px; font-size: .88em; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
.back { display: inline-block; margin: 24px 0 56px; color: var(--muted); font-size: .93rem; }
table { border-collapse: collapse; width: 100%; margin: 16px 0; font-size: .92rem; }
th, td { border: 1px solid var(--line); padding: 8px 12px; text-align: left; }
th { background: var(--code-bg); }
.tablewrap { overflow-x: auto; }