/* ==========================================================================
   复旦求是学院 · 在线课件 UI 设计系统 v1.0 —— 共享样式
   基于 t11 design-system.html 令牌；供 01~04 四页原型引用
   学术学院风：复旦深藏蓝 #0A2E6E + 金 #C9A063
   ========================================================================== */

/* ---------- 0. 设计令牌 ---------- */
:root{
  --fd-blue-950:#04132E;--fd-blue-900:#071E4C;--fd-blue-800:#0A2E6E;--fd-blue-700:#0C3A8C;
  --fd-blue-600:#10479F;--fd-blue-500:#1557B8;--fd-blue-400:#3B77D1;--fd-blue-300:#7CA3E2;
  --fd-blue-200:#B4CBF0;--fd-blue-100:#DCE7F9;--fd-blue-50:#F1F6FD;
  --fd-gold-700:#7E5C24;--fd-gold-600:#9C7A3B;--fd-gold-500:#C9A063;--fd-gold-400:#D8B885;
  --fd-gold-300:#E7D2AB;--fd-gold-200:#F0E3C9;--fd-gold-100:#F8F0DF;--fd-gold-50:#FBF7EE;
  --fd-gray-900:#182338;--fd-gray-800:#253149;--fd-gray-700:#35435F;--fd-gray-600:#516079;
  --fd-gray-500:#6E7C93;--fd-gray-400:#96A1B5;--fd-gray-300:#BCC4D3;--fd-gray-200:#D9DEE8;
  --fd-gray-100:#EDF0F5;--fd-gray-50:#F7F9FC;
  --fd-success-700:#116B40;--fd-success-500:#219653;--fd-success-bg:#E9F6EF;
  --fd-danger-700:#A32323;--fd-danger-500:#C93A3A;--fd-danger-bg:#FBEFEF;
  --fd-warning-700:#8A5300;--fd-warning-500:#C77E14;--fd-warning-bg:#FFF5E4;--fd-info-bg:#EAF1FC;
  --fd-color-primary:var(--fd-blue-800);--fd-color-accent:var(--fd-gold-500);
  --fd-color-bg:var(--fd-gray-50);--fd-color-surface:#FFFFFF;
  --fd-color-border:var(--fd-gray-200);--fd-color-border-strong:var(--fd-gray-300);
  --fd-text-primary:var(--fd-gray-900);--fd-text-secondary:var(--fd-gray-600);--fd-text-tertiary:var(--fd-gray-400);
  --fd-font-serif:"Source Han Serif SC","Noto Serif SC","思源宋体","Songti SC","STSong","SimSun",Georgia,serif;
  --fd-font-sans:"Source Han Sans SC","Noto Sans SC","思源黑体","PingFang SC","Hiragino Sans GB","Microsoft YaHei","Helvetica Neue",Arial,sans-serif;
  --fd-font-mono:"JetBrains Mono","SF Mono","Cascadia Mono",Consolas,monospace;
  --fd-text-display:2.5rem;--fd-text-h1:2rem;--fd-text-h2:1.5rem;--fd-text-h3:1.25rem;--fd-text-h4:1.125rem;
  --fd-text-body-lg:1.0625rem;--fd-text-body:1rem;--fd-text-body-sm:0.875rem;--fd-text-caption:0.8125rem;--fd-text-micro:0.75rem;
  --fd-leading-heading:1.35;--fd-leading-body:1.75;--fd-leading-dense:1.5;
  --fd-space-1:4px;--fd-space-2:8px;--fd-space-3:12px;--fd-space-4:16px;--fd-space-5:24px;
  --fd-space-6:32px;--fd-space-7:40px;--fd-space-8:48px;--fd-space-9:64px;--fd-space-10:80px;
  --fd-radius-xs:4px;--fd-radius-sm:6px;--fd-radius-md:10px;--fd-radius-lg:14px;--fd-radius-xl:20px;--fd-radius-full:9999px;
  --fd-shadow-sm:0 1px 2px rgba(10,46,110,.06);--fd-shadow-md:0 4px 14px rgba(10,46,110,.09);
  --fd-shadow-lg:0 10px 30px rgba(10,46,110,.14);--fd-shadow-gold:0 4px 16px rgba(201,160,99,.32);
  --fd-shadow-focus:0 0 0 3px rgba(10,46,110,.14);
  --fd-z-base:0;--fd-z-nav:100;--fd-z-dropdown:200;--fd-z-sticky:300;--fd-z-overlay:400;--fd-z-toast:500;
  --fd-dur-fast:.15s;--fd-dur-base:.25s;--fd-ease:cubic-bezier(.4,0,.2,1);
}

/* ---------- 1. 基础 ---------- */
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{font-size:16px;-webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;scroll-behavior:smooth}
body{font-family:var(--fd-font-sans);color:var(--fd-text-primary);background:var(--fd-color-bg);line-height:var(--fd-leading-body);font-size:var(--fd-text-body)}
img,svg{display:block;max-width:100%}
a{color:var(--fd-blue-600);text-decoration:none}
a:hover{text-decoration:underline}
h1,h2,h3,h4{font-family:var(--fd-font-serif);color:var(--fd-blue-900);line-height:var(--fd-leading-heading)}
::selection{background:rgba(201,160,99,.35)}
button{font-family:var(--fd-font-sans)}
.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.container{max-width:1200px;margin:0 auto;padding:0 var(--fd-space-5)}

/* 区块标题 */
.sec-head{display:flex;align-items:baseline;gap:var(--fd-space-3);margin-bottom:var(--fd-space-5)}
.sec-head .sec-no{font-family:var(--fd-font-serif);font-size:var(--fd-text-h3);font-weight:700;color:var(--fd-gold-500)}
.sec-head h2{font-size:var(--fd-text-h2);margin:0}
.sec-head .sec-en{font-size:var(--fd-text-micro);letter-spacing:.18em;color:var(--fd-text-tertiary);text-transform:uppercase}

/* 进场动画 */
.reveal{opacity:0;transform:translateY(18px);transition:opacity .55s var(--fd-ease),transform .55s var(--fd-ease)}
.reveal.in{opacity:1;transform:none}

/* ---------- 2. 品牌 ---------- */
.fd-brand{display:inline-flex;align-items:center;gap:12px;color:inherit;text-decoration:none}
.fd-brand:hover{text-decoration:none}
.fd-brand__seal{width:42px;height:42px;flex:0 0 auto;display:grid;place-items:center;font-family:var(--fd-font-serif);font-size:19px;font-weight:700;border:2px solid var(--fd-gold-500);border-radius:8px;background:linear-gradient(160deg,var(--fd-blue-900),var(--fd-blue-800));color:var(--fd-gold-300);box-shadow:var(--fd-shadow-sm);position:relative}
.fd-brand__seal::after{content:"";position:absolute;inset:3px;border:1px solid rgba(201,160,99,.55);border-radius:5px}
.fd-brand__text{display:flex;flex-direction:column;line-height:1.2}
.fd-brand__name{font-family:var(--fd-font-serif);font-size:19px;font-weight:700;letter-spacing:.18em;white-space:nowrap}
.fd-brand__sub{font-size:10px;letter-spacing:.34em;text-transform:uppercase}
.fd-brand--dark .fd-brand__name{color:#fff}
.fd-brand--dark .fd-brand__sub{color:var(--fd-gold-400)}
.fd-brand--light .fd-brand__name{color:var(--fd-blue-900)}
.fd-brand--light .fd-brand__sub{color:var(--fd-gold-600)}

/* ---------- 3. 顶部导航 ---------- */
.fd-navbar{position:sticky;top:0;z-index:var(--fd-z-nav);display:flex;align-items:center;gap:var(--fd-space-4);height:64px;padding:0 var(--fd-space-5);background:linear-gradient(90deg,var(--fd-blue-950),var(--fd-blue-800) 55%,var(--fd-blue-700));color:var(--fd-text-on-blue,#fff);box-shadow:var(--fd-shadow-md)}
.fd-navbar::after{content:"";position:absolute;left:0;right:0;bottom:0;height:3px;background:linear-gradient(90deg,transparent 4%,var(--fd-gold-500) 30%,var(--fd-gold-400) 70%,transparent 96%)}
.fd-navbar__divider{width:1px;height:26px;background:rgba(255,255,255,.22);flex:0 0 auto}
.fd-course-switch{appearance:none;-webkit-appearance:none;height:38px;padding:0 38px 0 14px;border:1px solid rgba(255,255,255,.28);border-radius:var(--fd-radius-md);background:rgba(255,255,255,.08) url("data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%23C9A063' stroke-width='1.6' fill='none' stroke-linecap='round'/%3E%3C/svg%3E") no-repeat right 14px center;color:#fff;font-size:var(--fd-text-body-sm);font-weight:500;cursor:pointer;transition:border-color var(--fd-dur-fast) var(--fd-ease),background var(--fd-dur-fast) var(--fd-ease)}
.fd-course-switch:hover{background-color:rgba(255,255,255,.14);border-color:var(--fd-gold-400)}
.fd-course-switch:focus{outline:none;box-shadow:0 0 0 3px rgba(201,160,99,.35)}
.fd-course-switch option{color:var(--fd-gray-900);background:#fff}
.fd-navbar__spacer{flex:1}
.fd-nav-search{position:relative;width:min(240px,26vw);flex:0 0 auto}
.fd-nav-search input{width:100%;height:38px;padding:0 12px 0 36px;border:1px solid rgba(255,255,255,.25);border-radius:var(--fd-radius-md);background:rgba(255,255,255,.09);color:#fff;font-size:var(--fd-text-body-sm);transition:all var(--fd-dur-fast) var(--fd-ease)}
.fd-nav-search input::placeholder{color:rgba(255,255,255,.55)}
.fd-nav-search input:focus{outline:none;border-color:var(--fd-gold-400);background:rgba(255,255,255,.16);box-shadow:0 0 0 3px rgba(201,160,99,.28)}
.fd-nav-search .fd-icon{position:absolute;left:12px;top:50%;transform:translateY(-50%);opacity:.7;pointer-events:none}
.fd-icon-btn{position:relative;width:38px;height:38px;display:grid;place-items:center;border:0;border-radius:var(--fd-radius-md);background:transparent;color:rgba(255,255,255,.85);cursor:pointer;transition:background var(--fd-dur-fast) var(--fd-ease)}
.fd-icon-btn:hover{background:rgba(255,255,255,.14);color:#fff}
.fd-icon-btn__dot{position:absolute;top:8px;right:9px;width:7px;height:7px;border-radius:50%;background:var(--fd-gold-400);box-shadow:0 0 0 2px var(--fd-blue-800)}
.fd-burger{display:none;width:38px;height:38px;place-items:center;border:0;border-radius:var(--fd-radius-md);background:rgba(255,255,255,.1);color:#fff;cursor:pointer}
.fd-user{display:flex;align-items:center;gap:10px;padding-left:var(--fd-space-4);border-left:1px solid rgba(255,255,255,.22)}
.fd-avatar{width:34px;height:34px;border-radius:50%;display:grid;place-items:center;font-family:var(--fd-font-serif);font-size:14px;font-weight:700;color:var(--fd-blue-900);background:linear-gradient(135deg,var(--fd-gold-300),var(--fd-gold-500));box-shadow:var(--fd-shadow-sm);flex:0 0 auto}
.fd-user__meta{display:flex;flex-direction:column;line-height:1.25}
.fd-user__name{font-size:var(--fd-text-body-sm);font-weight:600;color:#fff}
.fd-user__role{font-size:11px;color:rgba(255,255,255,.62)}

/* ---------- 4. 面包屑 ---------- */
.fd-crumbs{display:flex;align-items:center;gap:8px;flex-wrap:wrap;font-size:var(--fd-text-body-sm);color:var(--fd-text-tertiary)}
.fd-crumbs a{color:var(--fd-blue-700);transition:color var(--fd-dur-fast) var(--fd-ease)}
.fd-crumbs a:hover{color:var(--fd-blue-500);text-decoration:none}
.fd-crumbs__sep{color:var(--fd-gray-300);user-select:none}
.fd-crumbs__current{color:var(--fd-gray-800);font-weight:600}

/* ---------- 5. 标签 ---------- */
.fd-tag{display:inline-flex;align-items:center;gap:5px;height:24px;padding:0 11px;border-radius:var(--fd-radius-full);font-size:var(--fd-text-micro);font-weight:500;letter-spacing:.02em;white-space:nowrap;border:1px solid transparent}
.fd-tag--blue{background:var(--fd-blue-50);color:var(--fd-blue-800);border-color:var(--fd-blue-200)}
.fd-tag--gold{background:var(--fd-gold-50);color:var(--fd-gold-600);border-color:var(--fd-gold-300)}
.fd-tag--gray{background:var(--fd-gray-50);color:var(--fd-gray-600);border-color:var(--fd-gray-200)}
.fd-tag--success{background:var(--fd-success-bg);color:var(--fd-success-700);border-color:rgba(33,150,83,.3)}
.fd-tag--danger{background:var(--fd-danger-bg);color:var(--fd-danger-700);border-color:rgba(201,58,58,.3)}
.fd-tag--warning{background:var(--fd-warning-bg);color:var(--fd-warning-700);border-color:rgba(199,126,20,.3)}
.fd-tag--solid-blue{background:var(--fd-blue-800);color:#fff}
.fd-tag--solid-gold{background:var(--fd-gold-500);color:var(--fd-text-on-gold,#3A2A0E)}
.fd-tag__dot{width:6px;height:6px;border-radius:50%;background:currentColor}

/* ---------- 6. 按钮 ---------- */
.fd-btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;height:40px;padding:0 22px;border-radius:var(--fd-radius-md);border:1px solid transparent;font-size:var(--fd-text-body-sm);font-weight:600;letter-spacing:.02em;cursor:pointer;transition:all var(--fd-dur-fast) var(--fd-ease);white-space:nowrap;text-decoration:none}
.fd-btn:hover{text-decoration:none}
.fd-btn:focus-visible{outline:none;box-shadow:var(--fd-shadow-focus)}
.fd-btn--primary{background:var(--fd-blue-800);color:#fff;box-shadow:var(--fd-shadow-sm)}
.fd-btn--primary:hover{background:var(--fd-blue-700);box-shadow:var(--fd-shadow-md);transform:translateY(-1px)}
.fd-btn--primary:active{background:var(--fd-blue-900);transform:translateY(0)}
.fd-btn--gold{background:linear-gradient(135deg,var(--fd-gold-400),var(--fd-gold-500));color:var(--fd-text-on-gold,#3A2A0E);box-shadow:var(--fd-shadow-gold)}
.fd-btn--gold:hover{filter:brightness(1.05);box-shadow:0 6px 20px rgba(201,160,99,.42);transform:translateY(-1px)}
.fd-btn--secondary{background:var(--fd-color-surface);border-color:var(--fd-gray-300);color:var(--fd-gray-800)}
.fd-btn--secondary:hover{border-color:var(--fd-blue-500);color:var(--fd-blue-800);background:var(--fd-blue-50)}
.fd-btn--ghost{background:transparent;color:var(--fd-blue-800)}
.fd-btn--ghost:hover{background:var(--fd-blue-50)}
.fd-btn--sm{height:32px;padding:0 14px;font-size:var(--fd-text-micro);border-radius:var(--fd-radius-sm)}
.fd-btn--lg{height:48px;padding:0 30px;font-size:var(--fd-text-body);border-radius:var(--fd-radius-md)}
.fd-btn--block{display:flex;width:100%}
.fd-btn[disabled],.fd-btn--disabled{opacity:.5;pointer-events:none;box-shadow:none;transform:none}

/* ---------- 7. 进度条 ---------- */
.fd-progress{position:relative;height:8px;background:var(--fd-gray-100);border-radius:var(--fd-radius-full);overflow:hidden}
.fd-progress__bar{height:100%;border-radius:var(--fd-radius-full);background:linear-gradient(90deg,var(--fd-blue-700),var(--fd-blue-500));position:relative;transition:width .6s var(--fd-ease)}
.fd-progress--gold .fd-progress__bar{background:linear-gradient(90deg,var(--fd-gold-600),var(--fd-gold-400))}
.fd-progress--xs{height:5px}
.fd-progress--lg{height:12px}
.fd-progress__label{display:flex;justify-content:space-between;font-size:var(--fd-text-micro);color:var(--fd-text-secondary);margin-bottom:6px}
.fd-progress__label b{color:var(--fd-blue-800)}

/* ---------- 8. 折叠 ---------- */
.fd-details{border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-md);background:var(--fd-color-surface);overflow:hidden;transition:border-color var(--fd-dur-fast) var(--fd-ease)}
.fd-details[open]{border-color:var(--fd-gold-400);box-shadow:var(--fd-shadow-sm)}
.fd-details summary{list-style:none;display:flex;align-items:center;gap:10px;padding:13px 16px;cursor:pointer;user-select:none;font-size:var(--fd-text-body-sm);font-weight:600;color:var(--fd-blue-900)}
.fd-details summary::-webkit-details-marker{display:none}
.fd-details summary:hover{background:var(--fd-blue-50)}
.fd-details summary .fd-details__chev{width:8px;height:8px;border-right:2px solid var(--fd-gold-600);border-bottom:2px solid var(--fd-gold-600);transform:rotate(-45deg);transition:transform var(--fd-dur-base) var(--fd-ease);margin-left:auto;flex:0 0 auto}
.fd-details[open] summary .fd-details__chev{transform:rotate(45deg)}
.fd-details__body{padding:0 16px 14px 42px;font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary);line-height:var(--fd-leading-dense)}

/* ---------- 9. 侧栏/树 ---------- */
.fd-side{width:300px;flex:0 0 300px;background:var(--fd-color-surface);border-right:1px solid var(--fd-color-border);display:flex;flex-direction:column;align-self:stretch}
.fd-side__head{padding:var(--fd-space-5) var(--fd-space-4) var(--fd-space-4);border-bottom:1px solid var(--fd-gray-100)}
.fd-side__title{font-size:var(--fd-text-body-sm);font-weight:700;color:var(--fd-blue-900);display:flex;align-items:center;justify-content:space-between}
.fd-side__progress{display:flex;align-items:center;justify-content:space-between;font-size:var(--fd-text-micro);color:var(--fd-text-secondary);margin-top:var(--fd-space-2)}
.fd-side__progress b{color:var(--fd-blue-800)}
.fd-tree{list-style:none;padding:var(--fd-space-3) var(--fd-space-2) var(--fd-space-6);overflow:auto}
.fd-tree__group{border-bottom:1px solid var(--fd-gray-100)}
.fd-tree__group:last-child{border-bottom:0}
.fd-tree__summary{display:flex;align-items:center;gap:10px;padding:10px 10px;border-radius:var(--fd-radius-md);cursor:pointer;list-style:none;user-select:none}
.fd-tree__summary::-webkit-details-marker{display:none}
.fd-tree__summary:hover{background:var(--fd-gray-50)}
.fd-tree__chevron{width:8px;height:8px;border-right:2px solid var(--fd-gray-400);border-bottom:2px solid var(--fd-gray-400);transform:rotate(-45deg);transition:transform var(--fd-dur-base) var(--fd-ease);flex:0 0 auto}
.fd-tree__group[open] .fd-tree__chevron{transform:rotate(45deg)}
.fd-tree__ch{flex:1;font-size:var(--fd-text-body-sm);font-weight:600;color:var(--fd-gray-800)}
.fd-tree__count{font-size:var(--fd-text-micro);color:var(--fd-text-tertiary);background:var(--fd-gray-100);border-radius:var(--fd-radius-full);padding:1px 9px}
.fd-tree__items{list-style:none;padding:0 0 8px 24px}
.fd-tree__item{display:flex;align-items:center;gap:9px;padding:8px 10px;border-radius:var(--fd-radius-md);font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary);cursor:pointer;transition:all var(--fd-dur-fast) var(--fd-ease);position:relative;text-decoration:none}
.fd-tree__item:hover{background:var(--fd-blue-50);color:var(--fd-blue-800);text-decoration:none}
.fd-tree__item .fd-tree__dot{width:6px;height:6px;border-radius:50%;background:var(--fd-gray-300);flex:0 0 auto}
.fd-tree__item--done{color:var(--fd-text-tertiary)}
.fd-tree__item--done .fd-tree__dot{background:var(--fd-gold-500)}
.fd-tree__item--current{background:var(--fd-blue-50);color:var(--fd-blue-800);font-weight:600}
.fd-tree__item--current::before{content:"";position:absolute;left:-8px;top:6px;bottom:6px;width:4px;border-radius:2px;background:var(--fd-gold-500)}
.fd-tree__item--current .fd-tree__dot{background:var(--fd-blue-800)}
.fd-tree__item .fd-tree__dur{margin-left:auto;font-size:11px;color:var(--fd-text-tertiary)}

/* ---------- 10. 搜索框 ---------- */
.fd-search{position:relative;width:min(420px,100%)}
.fd-search__input{width:100%;height:46px;padding:0 46px 0 44px;border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-md);background:var(--fd-color-surface);font-size:var(--fd-text-body-sm);color:var(--fd-text-primary);transition:all var(--fd-dur-fast) var(--fd-ease);box-shadow:var(--fd-shadow-sm)}
.fd-search__input::placeholder{color:var(--fd-text-tertiary)}
.fd-search__input:hover{border-color:var(--fd-gray-300)}
.fd-search__input:focus{outline:none;border-color:var(--fd-blue-500);box-shadow:var(--fd-shadow-focus)}
.fd-search__icon{position:absolute;left:15px;top:50%;transform:translateY(-50%);color:var(--fd-gray-400);pointer-events:none}
.fd-search__kbd{position:absolute;right:13px;top:50%;transform:translateY(-50%);font-size:11px;color:var(--fd-text-tertiary);background:var(--fd-gray-100);border:1px solid var(--fd-gray-200);border-radius:4px;padding:1px 7px;pointer-events:none}

/* ---------- 11. 卡片 ---------- */
.fd-course{display:flex;gap:var(--fd-space-5);background:var(--fd-color-surface);border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-lg);padding:var(--fd-space-5);box-shadow:var(--fd-shadow-sm);transition:box-shadow var(--fd-dur-base) var(--fd-ease),transform var(--fd-dur-base) var(--fd-ease)}
.fd-course:hover{box-shadow:var(--fd-shadow-lg);transform:translateY(-2px)}
.fd-course__cover{position:relative;width:168px;height:118px;flex:0 0 auto;border-radius:var(--fd-radius-md);background:linear-gradient(150deg,var(--fd-blue-900) 10%,var(--fd-blue-700) 60%,var(--fd-blue-600));display:grid;place-items:center;overflow:hidden;box-shadow:var(--fd-shadow-sm)}
.fd-course__cover::before{content:"";position:absolute;right:-30px;top:-30px;width:110px;height:110px;border-radius:50%;border:14px solid rgba(201,160,99,.28)}
.fd-course__cover::after{content:"";position:absolute;left:0;bottom:0;right:0;height:3px;background:linear-gradient(90deg,var(--fd-gold-500),var(--fd-gold-300))}
.fd-course__monogram{font-family:var(--fd-font-serif);font-size:56px;font-weight:900;color:rgba(255,255,255,.94);text-shadow:0 4px 16px rgba(4,19,46,.4)}
.fd-course__period{position:absolute;top:10px;left:0;background:var(--fd-gold-500);color:var(--fd-text-on-gold,#3A2A0E);font-size:11px;font-weight:700;letter-spacing:.08em;padding:3px 12px 3px 10px;border-radius:0 var(--fd-radius-full) var(--fd-radius-full) 0;box-shadow:var(--fd-shadow-sm)}
.fd-course__body{flex:1;min-width:0;display:flex;flex-direction:column}
.fd-course__title{font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);font-weight:700;color:var(--fd-blue-900);margin-bottom:6px}
.fd-course__sub{font-size:var(--fd-text-caption);color:var(--fd-text-secondary);margin-bottom:var(--fd-space-3)}
.fd-course__stats{display:flex;gap:var(--fd-space-4);flex-wrap:wrap;font-size:var(--fd-text-micro);color:var(--fd-text-secondary);margin-bottom:var(--fd-space-3)}
.fd-course__stats b{color:var(--fd-blue-800)}
.fd-course__foot{display:flex;align-items:center;justify-content:space-between;gap:var(--fd-space-4);margin-top:auto}
.fd-course__progress{flex:1;max-width:300px}
.fd-course__progress .fd-progress__label{margin-bottom:4px}

.fd-kcard{background:var(--fd-color-surface);border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-lg);padding:var(--fd-space-5);box-shadow:var(--fd-shadow-sm);transition:box-shadow var(--fd-dur-base) var(--fd-ease)}
.fd-kcard:hover{box-shadow:var(--fd-shadow-md)}
.fd-kcard__head{display:flex;align-items:center;gap:var(--fd-space-3);margin-bottom:var(--fd-space-3);flex-wrap:wrap}
.fd-kcard__index{width:38px;height:38px;flex:0 0 auto;display:grid;place-items:center;font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);font-weight:700;color:var(--fd-blue-800);background:var(--fd-blue-50);border:1px solid var(--fd-blue-200);border-radius:var(--fd-radius-md)}
.fd-kcard__title{font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);font-weight:600;color:var(--fd-blue-900)}
.fd-kcard__meta{display:flex;align-items:center;gap:var(--fd-space-2);flex-wrap:wrap;margin-left:auto}
.fd-kcard__points{list-style:none;display:grid;gap:6px;margin:var(--fd-space-3) 0 var(--fd-space-4)}
.fd-kcard__points li{position:relative;padding-left:18px;font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary)}
.fd-kcard__points li::before{content:"";position:absolute;left:2px;top:9px;width:7px;height:7px;border-radius:2px;background:var(--fd-gold-500);transform:rotate(45deg)}
.fd-kcard__foot{display:flex;align-items:center;gap:var(--fd-space-3);border-top:1px dashed var(--fd-gray-200);padding-top:var(--fd-space-3)}

.fd-ecard{background:var(--fd-color-surface);border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-lg);padding:var(--fd-space-5);box-shadow:var(--fd-shadow-sm);border-left:4px solid var(--fd-gold-500)}
.fd-ecard__head{display:flex;align-items:center;gap:10px;margin-bottom:var(--fd-space-3);flex-wrap:wrap}
.fd-ecard__badge{display:inline-flex;align-items:center;gap:6px;background:var(--fd-gold-500);color:var(--fd-text-on-gold,#3A2A0E);font-size:var(--fd-text-micro);font-weight:700;letter-spacing:.08em;padding:3px 12px;border-radius:var(--fd-radius-sm);box-shadow:var(--fd-shadow-sm)}
.fd-ecard__source{font-size:var(--fd-text-micro);color:var(--fd-text-tertiary)}
.fd-ecard__stem{font-size:var(--fd-text-body);line-height:var(--fd-leading-body);margin-bottom:var(--fd-space-3)}

.fd-qcard{background:var(--fd-color-surface);border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-lg);padding:var(--fd-space-5);box-shadow:var(--fd-shadow-sm)}
.fd-qcard__head{display:flex;align-items:center;gap:10px;margin-bottom:var(--fd-space-3);flex-wrap:wrap}
.fd-qcard__no{font-family:var(--fd-font-serif);font-weight:700;color:var(--fd-blue-800);font-size:var(--fd-text-body-sm);background:var(--fd-blue-50);border:1px solid var(--fd-blue-200);padding:2px 12px;border-radius:var(--fd-radius-full)}
.fd-qcard__stem{font-size:var(--fd-text-body);line-height:var(--fd-leading-body);margin-bottom:var(--fd-space-4)}
.fd-qcard__options{display:grid;gap:8px}
.fd-option{display:flex;align-items:flex-start;gap:11px;padding:11px 14px;border:1px solid var(--fd-gray-200);border-radius:var(--fd-radius-md);cursor:pointer;font-size:var(--fd-text-body-sm);color:var(--fd-text-primary);transition:all var(--fd-dur-fast) var(--fd-ease);background:var(--fd-color-surface)}
.fd-option:hover{border-color:var(--fd-blue-400);background:var(--fd-blue-50)}
.fd-option__key{width:24px;height:24px;flex:0 0 auto;display:grid;place-items:center;border-radius:50%;background:var(--fd-gray-100);font-size:13px;font-weight:700;color:var(--fd-gray-600);transition:all var(--fd-dur-fast) var(--fd-ease)}
.fd-option--selected{border-color:var(--fd-blue-500);background:var(--fd-blue-50)}
.fd-option--selected .fd-option__key{background:var(--fd-blue-800);color:#fff}
.fd-option--correct{border-color:var(--fd-success-500);background:var(--fd-success-bg)}
.fd-option--correct .fd-option__key{background:var(--fd-success-500);color:#fff}
.fd-option--wrong{border-color:var(--fd-danger-500);background:var(--fd-danger-bg)}
.fd-option--wrong .fd-option__key{background:var(--fd-danger-500);color:#fff}
.fd-qcard__actions{display:flex;gap:10px;margin-top:var(--fd-space-4);align-items:center;flex-wrap:wrap}
.fd-answer{display:none;margin-top:var(--fd-space-4);border-top:1px dashed var(--fd-gray-200);padding-top:var(--fd-space-4);animation:fd-fade .3s var(--fd-ease)}
.fd-answer--show{display:block}
.fd-answer__head{display:flex;align-items:center;gap:8px;margin-bottom:10px;flex-wrap:wrap}
.fd-explanation{font-size:var(--fd-text-body-sm);line-height:var(--fd-leading-dense);color:var(--fd-text-secondary);background:var(--fd-gray-50);border-radius:var(--fd-radius-md);padding:12px 14px}
@keyframes fd-fade{from{opacity:0;transform:translateY(-6px)}to{opacity:1;transform:none}}
@keyframes fd-pulse{0%,100%{transform:scale(1)}50%{transform:scale(1.06)}}

/* 标记按钮（错题） */
.fd-flag{display:inline-flex;align-items:center;gap:6px;height:32px;padding:0 14px;border-radius:var(--fd-radius-sm);border:1px solid var(--fd-gray-300);background:var(--fd-color-surface);color:var(--fd-gray-600);font-size:var(--fd-text-micro);font-weight:600;cursor:pointer;transition:all var(--fd-dur-fast) var(--fd-ease)}
.fd-flag:hover{border-color:var(--fd-gold-500);color:var(--fd-gold-600)}
.fd-flag.is-on{background:var(--fd-gold-50);border-color:var(--fd-gold-500);color:var(--fd-gold-600)}
.fd-flag.is-on svg{fill:var(--fd-gold-500)}

/* ---------- 12. 页脚 ---------- */
.fd-footer{background:linear-gradient(180deg,var(--fd-blue-950),var(--fd-blue-900));color:rgba(255,255,255,.72);margin-top:var(--fd-space-10)}
.fd-footer__inner{max-width:1200px;margin:0 auto;padding:var(--fd-space-8) var(--fd-space-5) var(--fd-space-6);display:flex;gap:var(--fd-space-8);flex-wrap:wrap;align-items:flex-start}
.fd-footer__brand{flex:1;min-width:240px}
.fd-footer__cols{display:flex;gap:var(--fd-space-8);flex-wrap:wrap}
.fd-footer h4{color:var(--fd-gold-300);font-size:var(--fd-text-body-sm);margin-bottom:10px;font-family:var(--fd-font-sans)}
.fd-footer ul{list-style:none;display:grid;gap:6px;font-size:var(--fd-text-body-sm)}
.fd-footer a{color:rgba(255,255,255,.72)}
.fd-footer a:hover{color:var(--fd-gold-300);text-decoration:none}
.fd-footer__bar{max-width:1200px;margin:0 auto;padding:14px var(--fd-space-5);border-top:1px solid rgba(255,255,255,.12);font-size:var(--fd-text-micro);color:rgba(255,255,255,.5);display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}

/* ==========================================================================
   页面一：首页
   ========================================================================== */
.hero{position:relative;background:linear-gradient(150deg,var(--fd-blue-950) 0%,var(--fd-blue-900) 45%,var(--fd-blue-800) 100%);color:#fff;overflow:hidden}
.hero::before{content:"";position:absolute;right:-120px;top:-120px;width:460px;height:460px;border-radius:50%;border:56px solid rgba(201,160,99,.12)}
.hero::after{content:"求是";position:absolute;right:8%;bottom:-40px;font-family:var(--fd-font-serif);font-size:220px;font-weight:900;color:rgba(255,255,255,.045);line-height:1;user-select:none;pointer-events:none}
.hero__inner{position:relative;z-index:1;max-width:1200px;margin:0 auto;padding:var(--fd-space-10) var(--fd-space-5) var(--fd-space-9);display:grid;grid-template-columns:1.15fr .85fr;gap:var(--fd-space-8);align-items:center}
.hero__eyebrow{display:inline-flex;align-items:center;gap:8px;font-size:var(--fd-text-micro);letter-spacing:.28em;color:var(--fd-gold-300);border:1px solid rgba(201,160,99,.45);border-radius:var(--fd-radius-full);padding:5px 16px;background:rgba(201,160,99,.1);margin-bottom:var(--fd-space-5)}
.hero__title{font-family:var(--fd-font-serif);font-size:clamp(2rem,4.4vw,3.2rem);font-weight:900;color:#fff;letter-spacing:.06em;line-height:1.25;margin-bottom:var(--fd-space-4)}
.hero__title em{font-style:normal;color:var(--fd-gold-400)}
.hero__slogan{font-family:var(--fd-font-serif);font-size:var(--fd-text-h3);color:var(--fd-gold-200);letter-spacing:.3em;margin-bottom:var(--fd-space-4)}
.hero__desc{font-size:var(--fd-text-body-lg);color:rgba(255,255,255,.82);max-width:560px;margin-bottom:var(--fd-space-6);line-height:1.8}
.hero__stats{display:flex;gap:var(--fd-space-6);flex-wrap:wrap;margin-bottom:var(--fd-space-6)}
.hero__stat b{display:block;font-family:var(--fd-font-serif);font-size:var(--fd-text-h1);font-weight:700;color:var(--fd-gold-400);line-height:1.2}
.hero__stat span{font-size:var(--fd-text-caption);color:rgba(255,255,255,.66)}
.hero__cta{display:flex;gap:var(--fd-space-3);flex-wrap:wrap}
.hero__card{background:rgba(255,255,255,.06);border:1px solid rgba(255,255,255,.16);border-radius:var(--fd-radius-xl);padding:var(--fd-space-5);backdrop-filter:blur(6px);box-shadow:var(--fd-shadow-lg)}
.hero__card-head{display:flex;align-items:center;justify-content:space-between;margin-bottom:var(--fd-space-4)}
.hero__card-title{font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);color:#fff;display:flex;align-items:center;gap:10px}
.hero__card-body{display:grid;gap:12px}
.hero__mini{display:flex;align-items:center;gap:12px;background:rgba(255,255,255,.07);border-radius:var(--fd-radius-md);padding:10px 14px}
.hero__mini .fd-tag{flex:0 0 auto}
.hero__mini-name{flex:1;font-size:var(--fd-text-body-sm);color:rgba(255,255,255,.9)}
.hero__mini-bar{width:110px}

.home-sec{padding:var(--fd-space-9) 0 var(--fd-space-4)}
.home-sec--gray{background:var(--fd-color-surface);border-top:1px solid var(--fd-color-border);border-bottom:1px solid var(--fd-color-border)}
.course-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(520px,1fr));gap:var(--fd-space-5)}

.continue-card{display:flex;gap:var(--fd-space-5);background:linear-gradient(135deg,var(--fd-blue-50),var(--fd-gold-50));border:1px solid var(--fd-blue-200);border-radius:var(--fd-radius-lg);padding:var(--fd-space-5);align-items:center;box-shadow:var(--fd-shadow-sm)}
.continue-card__icon{width:56px;height:56px;flex:0 0 auto;border-radius:var(--fd-radius-md);background:linear-gradient(135deg,var(--fd-blue-800),var(--fd-blue-600));display:grid;place-items:center;color:var(--fd-gold-300);box-shadow:var(--fd-shadow-md)}
.continue-card__body{flex:1;min-width:0}
.continue-card__title{font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);color:var(--fd-blue-900);margin-bottom:4px}
.continue-card__sub{font-size:var(--fd-text-caption);color:var(--fd-text-secondary);margin-bottom:10px}
.continue-card__progress{max-width:340px}

/* ==========================================================================
   页面二：课程目录
   ========================================================================== */
.catalog-hero{padding:var(--fd-space-7) 0 var(--fd-space-6);background:linear-gradient(150deg,var(--fd-blue-950),var(--fd-blue-800));color:#fff}
.catalog-hero h1{color:#fff;font-size:var(--fd-text-h1);margin:var(--fd-space-3) 0 6px}
.catalog-hero p{color:rgba(255,255,255,.8);font-size:var(--fd-text-body)}
.catalog-tabs{display:inline-flex;gap:4px;background:var(--fd-gray-100);border-radius:var(--fd-radius-md);padding:4px;margin-bottom:var(--fd-space-6)}
.catalog-tabs button{border:0;background:transparent;padding:9px 26px;border-radius:var(--fd-radius-sm);font-size:var(--fd-text-body-sm);font-weight:600;color:var(--fd-text-secondary);cursor:pointer;transition:all var(--fd-dur-fast) var(--fd-ease)}
.catalog-tabs button.is-on{background:var(--fd-blue-800);color:#fff;box-shadow:var(--fd-shadow-sm)}
.catalog-pane{display:none;animation:fd-fade .35s var(--fd-ease)}
.catalog-pane.is-on{display:block}
.chapter-card{background:var(--fd-color-surface);border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-lg);box-shadow:var(--fd-shadow-sm);overflow:hidden;margin-bottom:var(--fd-space-4);transition:box-shadow var(--fd-dur-base) var(--fd-ease)}
.chapter-card:hover{box-shadow:var(--fd-shadow-md)}
.chapter-card__head{display:flex;align-items:center;gap:14px;padding:16px 20px;cursor:pointer;list-style:none;transition:background var(--fd-dur-fast) var(--fd-ease)}
.chapter-card__head::-webkit-details-marker{display:none}
.chapter-card__head:hover{background:var(--fd-blue-50)}
.chapter-card__no{width:40px;height:40px;flex:0 0 auto;display:grid;place-items:center;font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);font-weight:700;color:var(--fd-blue-800);background:var(--fd-blue-50);border:1px solid var(--fd-blue-200);border-radius:var(--fd-radius-md)}
.chapter-card__name{flex:1;font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);font-weight:600;color:var(--fd-blue-900)}
.chapter-card__meta{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.chapter-card__chev{width:9px;height:9px;border-right:2px solid var(--fd-gold-600);border-bottom:2px solid var(--fd-gold-600);transform:rotate(-45deg);transition:transform var(--fd-dur-base) var(--fd-ease)}
.chapter-card[open] .chapter-card__chev{transform:rotate(45deg)}
.chapter-card__body{padding:4px 20px 18px 74px;display:grid;gap:8px}
.chapter-card__lesson{display:flex;align-items:center;gap:10px;padding:9px 14px;border-radius:var(--fd-radius-md);font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary);text-decoration:none;transition:all var(--fd-dur-fast) var(--fd-ease);border:1px solid transparent}
.chapter-card__lesson:hover{background:var(--fd-blue-50);color:var(--fd-blue-800);text-decoration:none;border-color:var(--fd-blue-200)}
.chapter-card__lesson .fd-tag{margin-left:auto}
.chapter-card__lesson--cur{background:var(--fd-blue-50);border-color:var(--fd-blue-200);color:var(--fd-blue-800);font-weight:600}

.kp-nav{display:flex;flex-wrap:wrap;gap:10px}
.kp-nav a{display:inline-flex;align-items:center;gap:6px;padding:8px 16px;border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-full);background:var(--fd-color-surface);color:var(--fd-gray-700);font-size:var(--fd-text-body-sm);transition:all var(--fd-dur-fast) var(--fd-ease)}
.kp-nav a:hover{background:var(--fd-gold-50);border-color:var(--fd-gold-400);color:var(--fd-gold-600);text-decoration:none;transform:translateY(-1px)}

/* ==========================================================================
   页面三：章节学习
   ========================================================================== */
.learn-shell{display:flex;min-height:calc(100vh - 64px)}
.reading-progress{position:fixed;top:64px;left:0;right:0;height:3px;z-index:var(--fd-z-sticky);background:transparent;pointer-events:none}
.reading-progress__bar{height:100%;width:0;background:linear-gradient(90deg,var(--fd-gold-600),var(--fd-gold-400));box-shadow:0 0 8px rgba(201,160,99,.6);transition:width .1s linear}
.learn-main{flex:1;min-width:0;padding:var(--fd-space-6) var(--fd-space-7) var(--fd-space-10)}
.learn-title{font-size:var(--fd-text-h1);color:var(--fd-blue-900);margin:var(--fd-space-3) 0 6px}
.learn-sub{font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary);margin-bottom:var(--fd-space-5)}
.learn-meta{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:var(--fd-space-6);align-items:center}
.kp-block{background:var(--fd-color-surface);border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-lg);padding:var(--fd-space-6);box-shadow:var(--fd-shadow-sm);margin-bottom:var(--fd-space-5)}
.kp-block h3{font-size:var(--fd-text-h3);color:var(--fd-blue-900);margin-bottom:var(--fd-space-3);display:flex;align-items:center;gap:10px}
.kp-block h3 .kp-dot{width:10px;height:10px;border-radius:2px;background:var(--fd-gold-500);transform:rotate(45deg);flex:0 0 auto}
.kp-block h4{font-size:var(--fd-text-h4);margin:var(--fd-space-4) 0 var(--fd-space-2);color:var(--fd-blue-800)}
.kp-block ul{list-style:none;display:grid;gap:8px}
.kp-block ul li{position:relative;padding-left:20px;font-size:var(--fd-text-body);line-height:var(--fd-leading-body);color:var(--fd-text-primary)}
.kp-block ul li::before{content:"";position:absolute;left:3px;top:12px;width:7px;height:7px;border-radius:2px;background:var(--fd-gold-500);transform:rotate(45deg)}
.kp-block .formula{font-family:var(--fd-font-serif);background:var(--fd-blue-50);border:1px solid var(--fd-blue-100);border-left:3px solid var(--fd-blue-800);border-radius:var(--fd-radius-md);padding:14px 18px;margin:var(--fd-space-3) 0;font-size:var(--fd-text-body-lg);color:var(--fd-blue-900);overflow-x:auto}
.kp-block .formula .katex{font-size:1.06em}
.learn-nav{display:flex;justify-content:space-between;gap:var(--fd-space-3);margin-top:var(--fd-space-6)}
.learn-nav__box{display:inline-flex;align-items:center;gap:12px;padding:14px 18px;border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-md);background:var(--fd-color-surface);color:var(--fd-gray-800);font-size:var(--fd-text-body-sm);transition:all var(--fd-dur-fast) var(--fd-ease);text-decoration:none}
.learn-nav__box:hover{border-color:var(--fd-blue-400);color:var(--fd-blue-800);text-decoration:none;box-shadow:var(--fd-shadow-md);transform:translateY(-1px)}
.learn-nav__box--next{flex-direction:row-reverse;text-align:right}
.learn-nav__dir{display:block;font-size:var(--fd-text-micro);color:var(--fd-text-tertiary)}
.learn-nav__name{font-weight:600}

/* ==========================================================================
   页面四：练习作答
   ========================================================================== */
.quiz-shell{display:flex;min-height:calc(100vh - 64px)}
.quiz-main{flex:1;min-width:0;padding:var(--fd-space-6) var(--fd-space-7) var(--fd-space-10);max-width:900px}
.quiz-title{font-size:var(--fd-text-h2);color:var(--fd-blue-900);margin:var(--fd-space-3) 0 4px}
.quiz-sub{font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary);margin-bottom:var(--fd-space-5)}
.answer-sheet{width:280px;flex:0 0 280px;background:var(--fd-color-surface);border-left:1px solid var(--fd-color-border);display:flex;flex-direction:column;align-self:stretch;position:sticky;top:64px;height:calc(100vh - 64px)}
.answer-sheet__head{padding:var(--fd-space-5) var(--fd-space-4) var(--fd-space-3);border-bottom:1px solid var(--fd-gray-100)}
.answer-sheet__grid{display:grid;grid-template-columns:repeat(5,1fr);gap:8px;padding:var(--fd-space-4);overflow:auto;flex:1}
.as-num{height:36px;display:grid;place-items:center;border-radius:var(--fd-radius-md);border:1px solid var(--fd-gray-200);background:var(--fd-color-surface);font-size:var(--fd-text-body-sm);font-weight:600;color:var(--fd-gray-700);cursor:pointer;transition:all var(--fd-dur-fast) var(--fd-ease);font-family:var(--fd-font-serif)}
.as-num:hover{border-color:var(--fd-blue-400);color:var(--fd-blue-800)}
.as-num--cur{border-color:var(--fd-blue-800);background:var(--fd-blue-800);color:#fff;box-shadow:var(--fd-shadow-sm)}
.as-num--done{border-color:var(--fd-success-500);background:var(--fd-success-bg);color:var(--fd-success-700)}
.as-num--wrong{border-color:var(--fd-danger-500);background:var(--fd-danger-bg);color:var(--fd-danger-700)}
.as-num--flag{border-color:var(--fd-gold-500);background:var(--fd-gold-50);color:var(--fd-gold-600)}
.answer-sheet__legend{display:flex;gap:10px;flex-wrap:wrap;padding:10px var(--fd-space-4);border-top:1px solid var(--fd-gray-100);font-size:11px;color:var(--fd-text-secondary)}
.answer-sheet__legend span{display:inline-flex;align-items:center;gap:5px}
.answer-sheet__legend i{width:10px;height:10px;border-radius:3px;display:inline-block;border:1px solid var(--fd-gray-200)}
.result-panel{display:none;background:linear-gradient(135deg,var(--fd-blue-50),var(--fd-gold-50));border:1px solid var(--fd-blue-200);border-radius:var(--fd-radius-lg);padding:var(--fd-space-5);margin-bottom:var(--fd-space-5);animation:fd-fade .4s var(--fd-ease)}
.result-panel.is-show{display:block}
.result-panel__row{display:flex;gap:var(--fd-space-6);flex-wrap:wrap;align-items:center}
.result-panel__score{font-family:var(--fd-font-serif);font-size:var(--fd-text-h1);font-weight:700;color:var(--fd-blue-800)}
.result-panel__stats{display:flex;gap:var(--fd-space-5);flex-wrap:wrap;font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary)}
.result-panel__stats b{color:var(--fd-blue-800)}
.fd-toast{position:fixed;left:50%;bottom:34px;transform:translate(-50%,20px);background:var(--fd-blue-900);color:#fff;padding:11px 22px;border-radius:var(--fd-radius-full);font-size:var(--fd-text-body-sm);box-shadow:var(--fd-shadow-lg);opacity:0;pointer-events:none;transition:all .3s var(--fd-ease);z-index:var(--fd-z-toast)}
.fd-toast.is-show{opacity:1;transform:translate(-50%,0)}

/* ==========================================================================
   响应式
   ========================================================================== */
.fd-backdrop{position:fixed;inset:0;background:rgba(7,30,76,.5);opacity:0;pointer-events:none;transition:opacity .3s var(--fd-ease);z-index:calc(var(--fd-z-overlay) - 1)}
.fd-backdrop.is-open{opacity:1;pointer-events:auto}
/* 断点约定（对齐 spec）：>1280 桌面 / ≤1280 平板横屏·侧栏抽屉化 / ≤768 平板竖屏·单列 / ≤390 手机 */
@media (max-width:1280px){
  .fd-side{position:fixed;top:0;left:0;bottom:0;z-index:var(--fd-z-overlay);transform:translateX(-105%);transition:transform .32s var(--fd-ease);box-shadow:var(--fd-shadow-lg);width:300px}
  .fd-side.is-open{transform:translateX(0)}
  .fd-burger{display:grid}
  .answer-sheet{position:fixed;top:0;right:0;bottom:0;z-index:var(--fd-z-overlay);transform:translateX(105%);transition:transform .32s var(--fd-ease);box-shadow:var(--fd-shadow-lg)}
  .answer-sheet.is-open{transform:translateX(0)}
  .quiz-main{max-width:none}
}
@media (max-width:768px){
  .hero__inner{grid-template-columns:1fr;padding:var(--fd-space-8) var(--fd-space-5)}
  .course-grid{grid-template-columns:1fr}
  .learn-main{padding:var(--fd-space-5) var(--fd-space-4) var(--fd-space-8)}
  .quiz-main{padding:var(--fd-space-5) var(--fd-space-4) var(--fd-space-8)}
  .chapter-card__body{padding-left:20px}
  .fd-nav-search{display:none}
}
@media (max-width:390px){
  html{font-size:15px}
  .fd-user__meta{display:none}
  .fd-course-switch{max-width:150px;text-overflow:ellipsis;overflow:hidden;white-space:nowrap}
  .fd-course{flex-direction:column}
  .fd-course__cover{width:100%;height:92px}
  .fd-course__foot{flex-direction:column;align-items:stretch}
  .fd-course__progress{max-width:none}
  .fd-footer__inner{gap:var(--fd-space-5)}
}

/* ==========================================================================
   v1.1 扩展样式（完整在线课件）
   ========================================================================== */

/* 知识点小节分隔 */
.kp-section{display:flex;align-items:center;gap:12px;margin:var(--fd-space-7) 0 var(--fd-space-3)}
.kp-section::after{content:"";flex:1;height:1px;background:linear-gradient(90deg,var(--fd-gold-400),transparent)}
.kp-section .sec-no{font-family:var(--fd-font-serif);font-weight:700;color:var(--fd-gold-500)}
.kp-section h2{font-size:var(--fd-text-h2);margin:0;white-space:nowrap}

/* 知识点表格 */
.fd-table{width:100%;border-collapse:collapse;margin:var(--fd-space-3) 0;font-size:var(--fd-text-body-sm);overflow-x:auto;display:block}
.fd-table th,.fd-table td{border:1px solid var(--fd-gray-200);padding:8px 12px;text-align:left;vertical-align:top}
.fd-table th{background:var(--fd-blue-50);color:var(--fd-blue-900);font-weight:600;white-space:nowrap}
.fd-table tr:nth-child(even) td{background:var(--fd-gray-50)}

/* 例题选项 chips */
.fd-ecard__tags .fd-tag--blue{cursor:default}
.fd-ecard .fd-details{margin-top:var(--fd-space-3)}

/* 空状态 */
.empty-state{text-align:center;padding:var(--fd-space-9) var(--fd-space-5);color:var(--fd-text-tertiary);background:var(--fd-color-surface);border:1px dashed var(--fd-gray-300);border-radius:var(--fd-radius-lg)}
.empty-state .empty-state__icon{font-size:38px;margin-bottom:10px}

/* 搜索结果面板 */
.search-panel{position:absolute;top:calc(100% + 8px);left:0;right:0;background:var(--fd-color-surface);border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-md);box-shadow:var(--fd-shadow-lg);max-height:420px;overflow:auto;z-index:var(--fd-z-dropdown);display:none}
.search-panel.is-open{display:block}
.search-panel__group{padding:10px 14px;font-size:var(--fd-text-micro);font-weight:700;letter-spacing:.1em;color:var(--fd-gold-600);background:var(--fd-gold-50);position:sticky;top:0}
.search-panel__item{display:block;padding:10px 14px;border-bottom:1px solid var(--fd-gray-100);text-decoration:none;color:var(--fd-gray-800);font-size:var(--fd-text-body-sm);transition:background var(--fd-dur-fast) var(--fd-ease)}
.search-panel__item:hover{background:var(--fd-blue-50);text-decoration:none}
.search-panel__item b{color:var(--fd-blue-800)}
.search-panel__item small{display:block;color:var(--fd-text-tertiary);margin-top:2px}
.search-panel__empty{padding:18px;text-align:center;color:var(--fd-text-tertiary);font-size:var(--fd-text-body-sm)}

/* 页头搜索（目录页） */
.search-hero{position:relative;max-width:720px;margin:var(--fd-space-5) auto 0}

/* 知识点导航 chips */
.kp-nav{display:flex;flex-wrap:wrap;gap:10px;margin-top:var(--fd-space-4)}
.kp-nav a{display:inline-flex;align-items:center;gap:6px;padding:8px 16px;border:1px solid var(--fd-color-border);border-radius:var(--fd-radius-full);background:var(--fd-color-surface);color:var(--fd-gray-700);font-size:var(--fd-text-body-sm);transition:all var(--fd-dur-fast) var(--fd-ease)}
.kp-nav a:hover{background:var(--fd-gold-50);border-color:var(--fd-gold-400);color:var(--fd-gold-600);text-decoration:none;transform:translateY(-1px)}

/* 章节卡片内小节 */
.chapter-card__sec{display:flex;align-items:center;gap:10px;padding:7px 14px;border-radius:var(--fd-radius-md);font-size:var(--fd-text-body-sm);color:var(--fd-text-secondary);text-decoration:none;transition:background var(--fd-dur-fast) var(--fd-ease)}
.chapter-card__sec:hover{background:var(--fd-blue-50);color:var(--fd-blue-800);text-decoration:none}
.chapter-card__sec .fd-tag{margin-left:auto}
.chapter-card__sec--cur{background:var(--fd-blue-50);color:var(--fd-blue-800);font-weight:600}

/* 练习页选项禁用态 */
.fd-option--disabled{opacity:.45;pointer-events:none}

/* 答题卡数字（多题滚动） */
.answer-sheet__grid{grid-template-columns:repeat(6,1fr)}
.answer-sheet__grid.as-many{grid-template-columns:repeat(6,1fr)}

/* 评分面板扩展 */
.result-panel__ring{width:96px;height:96px;flex:0 0 auto;border-radius:50%;display:grid;place-items:center;background:conic-gradient(var(--fd-gold-500) calc(var(--pct,0)*1%),var(--fd-blue-100) 0);position:relative}
.result-panel__ring::after{content:"";position:absolute;inset:10px;border-radius:50%;background:var(--fd-color-surface)}
.result-panel__ring b{position:relative;z-index:1;font-family:var(--fd-font-serif);font-size:var(--fd-text-h4);color:var(--fd-blue-800)}
.result-panel__ring small{position:relative;z-index:1;display:block;text-align:center;font-size:10px;color:var(--fd-text-tertiary);margin-top:-4px}

/* 练习来源信息 */
.qcard-source{margin-top:var(--fd-space-2);font-size:var(--fd-text-micro);color:var(--fd-text-tertiary)}

/* 章节学习主区最大宽 */
.learn-main{max-width:920px}

/* 公式块横滚 */
.formula{overflow-x:auto}

/* 例题长题干 */
.fd-ecard__stem{white-space:normal}

/* 侧栏目录当前章节高亮 */
.fd-tree__summary.is-active{background:var(--fd-gold-50);border-left:3px solid var(--fd-gold-500)}

/* 首页课程卡片真实数据 */
.fd-course__stats span{display:inline-flex;align-items:center;gap:5px}

/* 顶部导航搜索建议面板（横跨导航） */
.fd-nav-search .search-panel{position:fixed;top:64px;right:var(--fd-space-5);left:auto;width:min(480px,90vw)}

/* 答题卡图例 */
.answer-sheet__legend span{white-space:nowrap}

/* 移动端 */
@media (max-width:768px){
  .chapter-card__body{padding-left:20px}
  .answer-sheet__grid{grid-template-columns:repeat(5,1fr)}
}
@media (max-width:390px){
  .kp-section h2{font-size:var(--fd-text-h3)}
  .fd-ecard__tags .fd-tag{margin-bottom:4px}
  .result-panel__row{flex-direction:column;align-items:flex-start;gap:var(--fd-space-3)}
}