/* ===========================================================
   em.css —— 电机电磁小课堂 · 专属样式
   依赖：energy.css（先引入），本文件只做「电磁模块」的扩展
   =========================================================== */

/* ---------- 目录页：带封面的小节卡 ---------- */
.dir-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:22px}
@media(max-width:900px){.dir-grid{grid-template-columns:repeat(2,1fr)}}
@media(max-width:640px){.dir-grid{grid-template-columns:1fr}}
.dir-card{position:relative;display:flex;flex-direction:column;border-radius:20px;overflow:hidden;
  background:var(--glass);border:1px solid var(--line);transition:.32s}
.dir-card:hover{transform:translateY(-8px);border-color:rgba(52,227,255,.55);
  box-shadow:0 26px 54px rgba(0,0,0,.45),0 0 34px rgba(52,227,255,.18)}
.dir-card .cover{position:relative;aspect-ratio:16/10;overflow:hidden;background:#08122b}
.dir-card .cover img{display:block;width:100%;height:100%;object-fit:cover;transition:.5s}
.dir-card:hover .cover img{transform:scale(1.07)}
.dir-card .cover::after{content:"";position:absolute;inset:0;
  background:linear-gradient(180deg,transparent 45%,rgba(5,8,24,.86))}
.dir-card .cover .badge{position:absolute;top:12px;left:12px;z-index:2;font-family:"Orbitron",sans-serif;
  font-size:11px;letter-spacing:.14em;color:#04122b;font-weight:800;padding:4px 11px;border-radius:999px;
  background:linear-gradient(120deg,var(--cyan),var(--blue))}
.dir-card .cover .stage{position:absolute;bottom:10px;left:14px;z-index:2;font-size:12px;
  color:#dff2ff;display:flex;align-items:center;gap:7px}
.dir-card .cover .stage i{width:7px;height:7px;border-radius:50%;background:var(--cyan);
  box-shadow:0 0 10px var(--cyan);font-style:normal}
.dir-card .body{padding:18px 20px 20px;display:flex;flex-direction:column;flex:1}
.dir-card h3{font-size:19px;font-weight:800;margin-bottom:7px}
.dir-card p{color:var(--muted);font-size:14px;flex:1}
.dir-card .go{margin-top:14px;display:inline-flex;align-items:center;gap:8px;font-weight:700;
  font-size:14px;color:var(--cyan)}
.dir-card .go svg{width:17px;height:17px;transition:.3s}
.dir-card:hover .go svg{transform:translateX(6px)}

/* ---------- 科普页：hero 大图 ---------- */
.em-hero-fig{margin:30px auto 0;max-width:920px;border-radius:22px;overflow:hidden;
  border:1px solid var(--line);box-shadow:0 30px 70px rgba(0,0,0,.5)}
.em-hero-fig img{display:block;width:100%;aspect-ratio:21/9;object-fit:cover}
.em-hero-fig figcaption{padding:11px 16px;font-size:12.5px;color:var(--muted);
  background:rgba(6,12,30,.92);border-top:1px solid var(--line);text-align:center}

/* ---------- 概念卡（图文并排） ---------- */
.concept-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:22px;margin-top:6px}
@media(max-width:820px){.concept-grid{grid-template-columns:1fr}}
.concept{display:flex;flex-direction:column;border-radius:20px;overflow:hidden;
  background:var(--glass);border:1px solid var(--line);transition:.3s}
.concept:hover{border-color:rgba(52,227,255,.5);transform:translateY(-5px);
  box-shadow:0 20px 44px rgba(0,0,0,.38)}
.concept .pic{aspect-ratio:16/9;overflow:hidden;background:#08122b}
.concept .pic img{display:block;width:100%;height:100%;object-fit:cover;transition:.5s}
.concept:hover .pic img{transform:scale(1.05)}
.concept .txt{padding:18px 20px 20px}
.concept h3{font-size:18px;margin-bottom:8px;display:flex;align-items:center;gap:9px}
.concept h3 .ic{width:26px;height:26px;flex:0 0 26px;border-radius:8px;display:grid;place-items:center;
  background:rgba(52,227,255,.12);border:1px solid rgba(52,227,255,.3)}
.concept h3 .ic svg{width:15px;height:15px}
.concept p{color:var(--muted);font-size:14px}
.concept p b{color:var(--cyan)}

/* ---------- 3D 控制条 ---------- */
.ctrlbar{display:flex;flex-wrap:wrap;gap:12px;justify-content:center;align-items:center;margin-top:22px}
.ctrl-btn{display:inline-flex;align-items:center;gap:9px;padding:11px 20px;border-radius:999px;
  font-size:14px;font-weight:700;color:#dff2ff;background:rgba(52,227,255,.10);
  border:1px solid rgba(52,227,255,.42);cursor:pointer;transition:.22s}
.ctrl-btn:hover{background:rgba(52,227,255,.2);transform:translateY(-2px)}
.ctrl-btn.on{color:#04122b;background:linear-gradient(120deg,var(--cyan),var(--blue));border-color:transparent;
  box-shadow:0 10px 26px rgba(52,227,255,.34)}
.ctrl-btn svg{width:17px;height:17px}
.ctrl-slide{display:inline-flex;align-items:center;gap:12px;padding:9px 20px;border-radius:999px;
  background:var(--glass);border:1px solid var(--line)}
.ctrl-slide span{font-size:13.5px;color:var(--muted);font-weight:600}
.ctrl-slide input[type=range]{-webkit-appearance:none;appearance:none;width:150px;height:5px;border-radius:99px;
  background:linear-gradient(90deg,var(--cyan),var(--blue));outline:none;cursor:pointer}
.ctrl-slide input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:19px;height:19px;
  border-radius:50%;background:#eaf1ff;border:3px solid var(--cyan);box-shadow:0 0 12px rgba(52,227,255,.7);cursor:pointer}

/* ---------- 磁场图例 ---------- */
.legend{display:flex;flex-wrap:wrap;gap:18px;justify-content:center;margin-top:16px;font-size:13px;color:var(--muted)}
.legend .lg{display:inline-flex;align-items:center;gap:8px}
.legend .sw{width:22px;height:5px;border-radius:99px}
.legend .sw.n{background:linear-gradient(90deg,#ff6a5e,#c23a34)}
.legend .sw.s{background:linear-gradient(90deg,#5a86ff,#2b4bb0)}
.legend .sw.f{background:linear-gradient(90deg,#34e3ff,#4d7cff)}
.legend .sw.c{background:linear-gradient(90deg,#ffcf3f,#d6893f)}

/* ---------- N/S 小徽章（正文内） ---------- */
.pill{display:inline-block;padding:1px 9px;border-radius:999px;font-size:12.5px;font-weight:800;
  font-family:"Orbitron",sans-serif;letter-spacing:.04em;vertical-align:middle}
.pill.n{color:#fff;background:linear-gradient(120deg,#ff6a5e,#c23a34)}
.pill.s{color:#fff;background:linear-gradient(120deg,#5a86ff,#2b4bb0)}

/* ---------- 实验步骤 ---------- */
.steps{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin-top:8px}
@media(max-width:760px){.steps{grid-template-columns:1fr}}
.step{padding:18px 20px;border-radius:16px;background:var(--glass);border:1px solid var(--line)}
.step .sn{font-family:"Orbitron",sans-serif;font-size:22px;font-weight:900;
  color:rgba(52,227,255,.55);margin-bottom:6px}
.step h4{font-size:15.5px;margin-bottom:6px}
.step p{color:var(--muted);font-size:13.8px}

/* ---------- 上/下一节导航 ---------- */
.modnav{display:flex;justify-content:space-between;gap:14px;margin-top:44px;flex-wrap:wrap}
.modnav a{flex:1;min-width:220px;display:flex;flex-direction:column;gap:4px;padding:16px 20px;border-radius:16px;
  background:var(--glass);border:1px solid var(--line);transition:.28s}
.modnav a:hover{border-color:rgba(52,227,255,.55);transform:translateY(-3px)}
.modnav a.next{text-align:right;align-items:flex-end}
.modnav a .k{font-family:"Orbitron",sans-serif;font-size:11px;letter-spacing:.16em;color:var(--muted)}
.modnav a .t{font-size:16px;font-weight:700;color:var(--text)}
.modnav a:hover .t{color:var(--cyan)}

/* ---------- 小结/要点条 ---------- */
.catch{margin-top:22px;padding:20px 24px;border-radius:18px;
  background:radial-gradient(circle at 0% 0%,rgba(52,227,255,.12),transparent 60%),var(--glass);
  border:1px solid var(--line)}
.catch h4{font-size:15px;color:var(--cyan);margin-bottom:10px;display:flex;align-items:center;gap:8px}
.catch ul{list-style:none;display:grid;gap:9px}
.catch li{display:flex;gap:10px;font-size:14.2px;color:#c7d5f2}
.catch li::before{content:"▸";color:var(--cyan);font-weight:900}

/* ---------- 无图部件卡的文字缩略格 ---------- */
.part-card .thumb-txt{display:grid;place-items:center;background:
  radial-gradient(circle at 40% 30%,rgba(52,227,255,.18),rgba(77,124,255,.06))}
.part-card .thumb-txt span{font-size:40px;filter:drop-shadow(0 0 12px rgba(52,227,255,.5))}

/* ---------- 提示小卡（对齐 note 风格但用于青色） ---------- */
.tipbox{margin-top:20px;padding:16px 20px;border-radius:14px;background:rgba(52,227,255,.07);
  border:1px solid rgba(52,227,255,.3);color:#cdeeff;font-size:14px}
.tipbox b{color:#fff}