/* ===== CSS Variables ===== */
:root {
  --brand-dark: #141413;
  --brand-light: #faf9f5;
  --brand-orange: #d97757;
  --brand-blue: #6a9bcc;
  --brand-green: #788c5d;
  --surface-0: #faf9f5;
  --surface-1: #ffffff;
  --surface-2: #f2f1ec;
  --text-primary: #141413;
  --text-secondary: #5c5b56;
  --text-tertiary: #9c9a91;
  --border-color: rgba(20,20,19,.1);
  --font-heading: 'Poppins', 'PingFang SC', sans-serif;
  --font-body: 'Lora', 'Noto Serif SC', Georgia, serif;
  --radius-sm: 6px;
  --radius: 10px;
  --radius-lg: 14px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,.06);
  --shadow-md: 0 4px 12px rgba(0,0,0,.07);
  --code-bg: #1e1e1e;
  --code-text: #d4d4d4;
}

@media(prefers-color-scheme:dark){
  :root:not([data-theme="light"]){
    --surface-0: #141413;
    --surface-1: #1a1a19;
    --surface-2: #232322;
    --text-primary: #faf9f5;
    --text-secondary: #b0aea5;
    --text-tertiary: #7a7870;
    --border-color: rgba(250,249,245,.08);
  }
}
html[data-theme="dark"]{
  --surface-0: #141413;
  --surface-1: #1a1a19;
  --surface-2: #232322;
  --text-primary: #faf9f5;
  --text-secondary: #b0aea5;
  --text-tertiary: #7a7870;
  --border-color: rgba(250,249,245,.08);
}

/* ===== Reset ===== */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;font-size:16px}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
body{font-family:var(--font-body);background:var(--surface-0);color:var(--text-primary);line-height:1.7;-webkit-font-smoothing:antialiased}
h1,h2,h3,h4,h5,h6{font-family:var(--font-heading);line-height:1.3;font-weight:700}
a{color:var(--brand-orange);text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%;display:block}

/* ===== Bilingual ===== */
html[lang="zh-CN"] [data-lang="en"],
html[lang="en"] [data-lang="zh"]{display:none!important}
html[lang="zh-CN"] span[data-lang="zh"],
html[lang="en"] span[data-lang="en"]{display:inline!important}
html[lang="zh-CN"] li[data-lang="zh"],
html[lang="en"] li[data-lang="en"]{display:list-item!important}

/* ===== Nav ===== */
.nav{position:sticky;top:0;z-index:100;backdrop-filter:blur(16px);-webkit-backdrop-filter:blur(16px);background:rgba(250,249,245,.8);border-bottom:1px solid var(--border-color);transition:background .2s}
html[data-theme="dark"] .nav{background:rgba(20,20,19,.8)}
@media(prefers-color-scheme:dark){:root:not([data-theme="light"]) .nav{background:rgba(20,20,19,.8)}}
.nav-inner{max-width:1200px;margin:0 auto;padding:0 24px;height:56px;display:flex;align-items:center;justify-content:space-between}
.nav-logo{display:flex;align-items:center;gap:8px;font-family:var(--font-heading);font-weight:700;font-size:1.1rem;color:var(--text-primary)}
.nav-logo svg{width:28px;height:28px}
.nav-links{display:flex;align-items:center;gap:20px;font-family:var(--font-heading);font-size:.85rem}
.nav-links a{color:var(--text-secondary);transition:color .15s}
.nav-links a:hover{color:var(--brand-orange);text-decoration:none}
.nav-links a.active{color:var(--brand-orange)}
.nav-btn{background:none;border:1px solid var(--border-color);border-radius:var(--radius-sm);padding:4px 10px;cursor:pointer;color:var(--text-secondary);font-family:var(--font-heading);font-size:.8rem;transition:all .15s;display:flex;align-items:center;gap:4px}
.nav-btn:hover{border-color:var(--brand-orange);color:var(--brand-orange)}
.nav-btn svg{width:16px;height:16px}

/* ===== Footer ===== */
.footer{background:var(--brand-dark);color:rgba(250,249,245,.7);padding:40px 0;text-align:center;font-size:.85rem}
.footer a{color:var(--brand-orange)}
.footer-inner{display:flex;flex-direction:column;align-items:center;gap:12px}

/* ===== Responsive nav ===== */
@media(max-width:768px){
  .nav-links a.nav-section-link{display:none}
}