/* ===== Spira AI 使用指南 · 暗色 / 未来感主题（仿 spira.ai） ===== */
:root{
  --bg:#0a0b10; --bg-2:#0e1018; --surface:#14161f; --surface-2:#191c27;
  --line:rgba(255,255,255,.08); --line-2:rgba(255,255,255,.05);
  --ink:#f3f5fa; --ink-2:#c4c9d6; --ink-3:#9aa1b2; --muted:#6b7180;
  --primary:#6c8cff; --primary-2:#8a6cff; --glow:rgba(108,140,255,.35);
  --ok:#48d597; --warn:#f0b541;
  --radius:14px;
  --mono:'JetBrains Mono',ui-monospace,Menlo,monospace;
  --sans:'Inter','Noto Sans SC',system-ui,sans-serif;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{font-family:var(--sans);background:var(--bg);color:var(--ink-2);
  -webkit-font-smoothing:antialiased;font-size:13.5px;line-height:1.65;letter-spacing:-.005em;
  background-image:radial-gradient(900px 500px at 80% -10%,rgba(108,140,255,.10),transparent 60%),radial-gradient(700px 460px at 0% 0%,rgba(138,108,255,.08),transparent 55%);
  background-attachment:fixed}
a{color:inherit;text-decoration:none}
::selection{background:rgba(108,140,255,.3);color:#fff}
::-webkit-scrollbar{width:8px;height:8px}
::-webkit-scrollbar-thumb{background:#2a2e3b;border-radius:4px}
strong{color:var(--ink);font-weight:600}
.muted{color:var(--muted)}

/* header */
.site-head{position:sticky;top:0;z-index:30;background:rgba(10,11,16,.72);backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}
.site-head .inner{max-width:1060px;margin:0 auto;padding:14px 32px;display:flex;align-items:center;gap:14px}
.site-head .brand{font-size:16px;font-weight:700;color:var(--ink);letter-spacing:-.02em}
.site-head .brand b{background:linear-gradient(90deg,var(--primary),var(--primary-2));-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.site-head nav{margin-left:auto;display:flex;gap:24px;font-size:13px}
.site-head nav a{color:var(--ink-3);font-weight:500;transition:.15s}
.site-head nav a:hover{color:var(--ink)}
@media(max-width:760px){.site-head nav{display:none}}

.container{max-width:1060px;margin:0 auto;padding:48px 32px 100px}
@media(max-width:760px){.container{padding:30px 18px 70px}}

/* hero */
.hero{padding:24px 0 10px;text-align:left}
.eyebrow{display:inline-block;font-size:11px;font-weight:600;color:var(--primary);text-transform:uppercase;letter-spacing:.14em;
  padding:5px 12px;border:1px solid rgba(108,140,255,.3);border-radius:999px;background:rgba(108,140,255,.08)}
.hero h1{font-size:46px;font-weight:700;color:var(--ink);letter-spacing:-.03em;line-height:1.08;margin-top:20px;
  background:linear-gradient(180deg,#ffffff,#b9c2e0);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.hero .lede{font-size:16px;color:var(--ink-3);max-width:720px;margin-top:18px;line-height:1.7}
@media(max-width:760px){.hero h1{font-size:32px}}

/* sections */
.block{margin-top:56px}
h2.sec{font-size:12px;font-weight:700;color:var(--primary);text-transform:uppercase;letter-spacing:.1em;margin:0 0 18px;display:flex;align-items:center;gap:10px}
h2.sec::before{content:"";width:22px;height:2px;border-radius:2px;background:linear-gradient(90deg,var(--primary),transparent)}
h3{font-size:16px;color:var(--ink);font-weight:600;letter-spacing:-.01em}
h4{font-size:14px;color:var(--ink);font-weight:600}
p{margin:8px 0;color:var(--ink-2)}
.block > p{color:var(--ink-3)}

/* grid + cards */
.grid{display:grid;gap:16px}
.g2{grid-template-columns:repeat(2,1fr)}
.g3{grid-template-columns:repeat(3,1fr)}
@media(max-width:820px){.g2,.g3{grid-template-columns:1fr}}
.card{background:linear-gradient(180deg,var(--surface),var(--bg-2));border:1px solid var(--line);border-radius:var(--radius);padding:22px 24px;transition:.18s}
.card:hover{border-color:rgba(108,140,255,.35);box-shadow:0 0 0 1px rgba(108,140,255,.1),0 18px 50px -20px var(--glow);transform:translateY(-2px)}
.card h4{margin-bottom:4px}
.card p{font-size:13px;color:var(--ink-3)}
.card.feat{grid-column:auto}

/* tags */
.tag{display:inline-flex;align-items:center;gap:5px;font-size:10.5px;font-weight:600;padding:3px 9px;border-radius:7px;
  color:var(--ink-2);background:rgba(255,255,255,.05);border:1px solid var(--line)}
.tag.b{color:#cdd8ff;border-color:rgba(108,140,255,.4);background:rgba(108,140,255,.14)}
.tag.a{color:#dcd0ff;border-color:rgba(138,108,255,.4);background:rgba(138,108,255,.14)}

/* steps */
.steps{display:grid;gap:12px;counter-reset:s}
.step{display:grid;grid-template-columns:34px 1fr;gap:16px;align-items:start;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:18px 20px}
.step .n{counter-increment:s;width:32px;height:32px;border-radius:10px;display:grid;place-items:center;font-weight:700;font-size:14px;
  color:#fff;background:linear-gradient(135deg,var(--primary),var(--primary-2));box-shadow:0 6px 20px -6px var(--glow)}
.step .n::before{content:counter(s)}
.step h4{margin-bottom:3px}
.step p{font-size:12.5px;margin:0;color:var(--ink-3)}

/* callout */
.callout{border-radius:var(--radius);padding:16px 18px;border:1px solid var(--line);background:var(--surface);font-size:13px;display:flex;gap:12px;align-items:flex-start;color:var(--ink-2)}
.callout .ic{font-size:14px;flex:none;line-height:1.5;color:var(--primary)}
.callout.b{background:rgba(108,140,255,.1);border-color:rgba(108,140,255,.28)}
.callout.g{background:rgba(72,213,151,.08);border-color:rgba(72,213,151,.25)}
.callout.g .ic{color:var(--ok)}
.callout b{color:var(--ink)}

/* clean list */
ul.clean{list-style:none;display:grid;gap:9px}
ul.clean li{position:relative;padding-left:20px;font-size:13px;color:var(--ink-2)}
ul.clean li::before{content:"→";position:absolute;left:0;color:var(--primary);font-weight:700}