/* ============================================================
   Lingua · 沉浸式多语种学习平台
   设计系统：ZONGYUAN-ROOT 稳态青蓝黑 · 联邦记忆内核节点
   节点：NODE-LINGUA-001 · DID-BR-000002
   ============================================================ */
:root{
  --bg:#0a0f1e;
  --bg2:#0f1730;
  --bg3:#141d3a;
  --panel:rgba(20,29,58,.72);
  --panel-solid:#131b36;
  --line:rgba(120,160,255,.18);
  --line2:rgba(120,160,255,.35);
  --ink:#e8eeff;
  --ink2:#aeb9dd;
  --muted:#7c89b8;
  --brand:#4c8dff;
  --brand2:#7a5cff;
  --ok:#3ddc97;
  --warn:#ffb454;
  --bad:#ff5c7a;
  --grad:linear-gradient(135deg,#4c8dff,#7a5cff);
  --shadow:0 10px 40px rgba(0,0,0,.45);
  --radius:16px;
  --font:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif;
}
*{box-sizing:border-box;margin:0;padding:0}
html,body{height:100%}
body{
  font-family:var(--font);background:
    radial-gradient(1200px 600px at 80% -10%,rgba(76,141,255,.14),transparent 60%),
    radial-gradient(900px 500px at -10% 110%,rgba(122,92,255,.12),transparent 60%),
    var(--bg);
  color:var(--ink);min-height:100vh;line-height:1.6;
}
a{color:var(--brand);text-decoration:none}
button{font-family:var(--font);cursor:pointer}
input,select,textarea{font-family:var(--font);color:var(--ink)}

/* ---------- 应用外壳 ---------- */
#app-shell{display:flex;min-height:100vh}
.sidebar{
  width:232px;background:var(--panel);border-right:1px solid var(--line);
  backdrop-filter:blur(14px);position:sticky;top:0;height:100vh;
  display:flex;flex-direction:column;flex-shrink:0;
}
.brand{display:flex;align-items:center;gap:10px;padding:22px 20px;border-bottom:1px solid var(--line)}
.brand-logo{width:34px;height:34px;border-radius:10px;background:var(--grad);display:grid;place-items:center;font-weight:800;color:#fff;font-size:15px}
.brand-name{font-weight:800;font-size:15px;letter-spacing:.3px}
.brand-sub{font-size:10px;color:var(--muted);margin-top:1px}
.nav{flex:1;padding:14px 12px;display:flex;flex-direction:column;gap:2px;overflow:auto}
.nav-item{
  display:flex;align-items:center;gap:12px;padding:11px 14px;border-radius:10px;color:var(--ink2);
  font-size:14px;transition:.15s;border:1px solid transparent;background:none;text-align:left;width:100%;
}
.nav-item:hover{background:rgba(76,141,255,.08);color:var(--ink)}
.nav-item.active{background:var(--grad);color:#fff;font-weight:600;box-shadow:0 4px 16px rgba(76,141,255,.3)}
.nav-item .ico{width:18px;text-align:center;font-size:16px}
.side-foot{padding:14px 20px;border-top:1px solid var(--line);font-size:11px;color:var(--muted)}
.side-foot .did{color:var(--brand2);font-weight:600}

/* ---------- 主内容 ---------- */
.main{flex:1;min-width:0;display:flex;flex-direction:column}
.topbar{
  position:sticky;top:0;z-index:50;display:flex;align-items:center;gap:16px;
  padding:16px 28px;background:rgba(10,15,30,.82);backdrop-filter:blur(14px);
  border-bottom:1px solid var(--line);
}
.topbar-title{font-size:16px;font-weight:700}
.topbar-spacer{flex:1}
.xp-pill{display:flex;align-items:center;gap:8px;background:var(--panel);border:1px solid var(--line);border-radius:999px;padding:6px 14px;font-size:13px;font-weight:600}
.xp-pill .lv{color:var(--brand);font-weight:800}
.btn-avatar{width:36px;height:36px;border-radius:50%;background:var(--grad);display:grid;place-items:center;font-weight:700;border:none;color:#fff}
.view{flex:1;padding:28px;max-width:1200px;width:100%;margin:0 auto}

/* ---------- 通用组件 ---------- */
.page-title{font-size:24px;font-weight:800;margin-bottom:6px}
.page-sub{color:var(--muted);font-size:14px;margin-bottom:24px}
.grid{display:grid;gap:16px}
.grid-2{grid-template-columns:repeat(2,1fr)}
.grid-3{grid-template-columns:repeat(3,1fr)}
.grid-4{grid-template-columns:repeat(4,1fr)}
.card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:20px;backdrop-filter:blur(8px)}
.card h3{font-size:15px;font-weight:700;margin-bottom:12px}
.card .hint{color:var(--muted);font-size:12px;margin-top:6px}
.stat{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:18px 20px}
.stat .v{font-size:26px;font-weight:800;color:var(--brand)}
.stat .l{color:var(--muted);font-size:12px;margin-top:2px}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:10px 18px;border-radius:10px;border:1px solid var(--line2);background:rgba(76,141,255,.12);color:var(--ink);font-size:14px;font-weight:600;transition:.15s}
.btn:hover{border-color:var(--brand);background:rgba(76,141,255,.2)}
.btn-primary{background:var(--grad);border:none;color:#fff;box-shadow:0 4px 18px rgba(76,141,255,.35)}
.btn-primary:hover{filter:brightness(1.08);background:var(--grad)}
.btn-ghost{background:transparent;border-color:var(--line)}
.btn-block{width:100%}
.btn[disabled]{opacity:.45;cursor:not-allowed}
.tag{display:inline-block;padding:3px 10px;border-radius:999px;font-size:11px;font-weight:600}
.tag-blue{background:rgba(76,141,255,.16);color:#7fb0ff}
.tag-green{background:rgba(61,220,151,.14);color:var(--ok)}
.tag-warn{background:rgba(255,180,84,.15);color:var(--warn)}
.tag-purple{background:rgba(122,92,255,.18);color:#b0a0ff}
.bar{height:8px;background:rgba(255,255,255,.08);border-radius:999px;overflow:hidden}
.bar i{display:block;height:100%;background:var(--grad);border-radius:999px;transition:width .5s}
.bar-green i{background:var(--ok)}
.empty{text-align:center;color:var(--muted);padding:40px 0;font-size:14px}
.divider{height:1px;background:var(--line);margin:16px 0}

/* ---------- 落地页 ---------- */
.landing-hero{text-align:center;padding:70px 20px 40px}
.landing-hero h1{font-size:44px;font-weight:900;line-height:1.15;margin-bottom:14px;letter-spacing:.5px}
.landing-hero h1 .g{background:var(--grad);-webkit-background-clip:text;background-clip:text;color:transparent}
.landing-hero p{color:var(--ink2);font-size:16px;max-width:640px;margin:0 auto 28px}
.hero-cta{display:flex;gap:14px;justify-content:center;flex-wrap:wrap}
.hero-meta{display:flex;gap:26px;justify-content:center;color:var(--muted);font-size:13px;margin-top:30px;flex-wrap:wrap}
.feature-card{border-top:2px solid transparent}
.feature-card:hover{border-top-color:var(--brand)}

/* ---------- 表单 ---------- */
.field{margin-bottom:14px}
.field label{display:block;font-size:13px;color:var(--ink2);margin-bottom:6px}
.field input,.field select,.field textarea{
  width:100%;padding:11px 14px;border-radius:10px;border:1px solid var(--line);background:var(--bg3);color:var(--ink);font-size:14px;outline:none;
}
.field input:focus,.field select:focus,.field textarea:focus{border-color:var(--brand)}
.form-card{max-width:420px;margin:20px auto}
.form-card h2{text-align:center;margin-bottom:6px}
.form-card .sub{text-align:center;color:var(--muted);margin-bottom:22px}

/* ---------- 课程卡 ---------- */
.course-card{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:18px;position:relative;transition:.15s}
.course-card:hover{border-color:var(--line2);transform:translateY(-2px)}
.course-card .lang{position:absolute;top:16px;right:16px}
.course-card h3{font-size:16px;margin:8px 0 4px}
.course-card .desc{color:var(--muted);font-size:13px}
.course-card .progress{display:flex;align-items:center;gap:8px;margin-top:14px;font-size:12px;color:var(--ink2)}
.course-card.locked{opacity:.5}
.course-card.locked .btn{opacity:.4}

/* ---------- 学习/四环节 ---------- */
.lesson-wrap{max-width:860px;margin:0 auto}
.lesson-steps{display:flex;gap:8px;margin-bottom:24px}
.step{flex:1;padding:8px;text-align:center;border-radius:10px;border:1px solid var(--line);color:var(--muted);font-size:13px}
.step.done{background:rgba(61,220,151,.12);border-color:var(--ok);color:var(--ok)}
.step.active{background:var(--grad);color:#fff;border-color:transparent;font-weight:600}
.flashcard{background:var(--bg3);border:1px solid var(--line2);border-radius:18px;padding:44px 28px;text-align:center;min-height:220px;cursor:pointer;transition:.2s}
.flashcard .front{font-size:34px;font-weight:800}
.flashcard .hint{color:var(--muted);font-size:12px;margin-top:18px}
.flashcard .back .word{font-size:26px;font-weight:700;color:var(--brand);margin-bottom:8px}
.flashcard .back .phon{color:var(--ink2)}
.flashcard .back .mean{color:var(--ink);margin-top:12px}
.opt-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:12px;margin-top:16px}
.opt{background:var(--bg3);border:1px solid var(--line);border-radius:12px;padding:14px;text-align:center;font-size:15px;transition:.15s}
.opt:hover{border-color:var(--brand)}
.opt.correct{background:rgba(61,220,151,.15);border-color:var(--ok);color:var(--ok)}
.opt.wrong{background:rgba(255,92,122,.15);border-color:var(--bad);color:var(--bad)}
.grammar-box{background:var(--bg3);border:1px solid var(--line);border-radius:14px;padding:20px;margin-bottom:14px}
.grammar-box .formula{font-size:18px;font-weight:700;color:var(--brand);margin-bottom:8px}
.speech-box{text-align:center;padding:30px;border:1px dashed var(--line2);border-radius:16px}
.speech-word{font-size:30px;font-weight:800;margin:12px 0}
.speech-score{font-size:22px;font-weight:800}
.audio-probe{background:var(--bg3);border-radius:14px;padding:20px;margin-bottom:14px}
.score-ring{width:120px;height:120px;margin:0 auto;position:relative}
.score-ring svg{transform:rotate(-90deg)}
.score-ring .num{position:absolute;inset:0;display:grid;place-items:center;font-size:26px;font-weight:800}

/* ---------- 训练营 ---------- */
.practice-type{border:1px solid var(--line);border-radius:14px;padding:18px;cursor:pointer;transition:.15s;background:var(--panel)}
.practice-type:hover{border-color:var(--brand)}
.practice-type .t{font-size:16px;font-weight:700;margin:8px 0 4px}

/* ---------- 社区 ---------- */
.post{background:var(--panel);border:1px solid var(--line);border-radius:var(--radius);padding:18px;margin-bottom:14px}
.post-head{display:flex;align-items:center;gap:12px;margin-bottom:10px}
.post-avatar{width:38px;height:38px;border-radius:50%;display:grid;place-items:center;font-weight:700;color:#fff}
.post-meta .n{font-weight:600;font-size:14px}
.post-meta .t{color:var(--muted);font-size:12px}
.post-body{color:var(--ink2);font-size:14px;margin-bottom:12px}
.post-actions{display:flex;gap:14px}
.post-actions button{background:none;border:none;color:var(--muted);font-size:13px;display:flex;align-items:center;gap:5px}
.post-actions button.liked{color:var(--bad)}
.comment{background:var(--bg3);border-radius:10px;padding:10px 12px;margin-top:8px;font-size:13px;color:var(--ink2)}

/* ---------- 成就 ---------- */
.badge{background:var(--panel);border:1px solid var(--line);border-radius:16px;padding:20px;text-align:center;transition:.15s}
.badge .icon{font-size:34px;margin-bottom:8px}
.badge .name{font-weight:700;font-size:14px}
.badge.locked{opacity:.35;filter:grayscale(.6)}
.badge.unlocked{border-color:var(--brand);background:linear-gradient(160deg,rgba(76,141,255,.12),rgba(122,92,255,.1))}
.rank-step{display:flex;align-items:center;gap:14px;background:var(--panel);border:1px solid var(--line);border-radius:12px;padding:14px 16px;margin-bottom:10px}
.rank-step .lv{font-size:22px;font-weight:900;color:var(--brand);min-width:50px}
.rank-step .cur{color:var(--muted);font-size:12px}

/* ---------- 雷达/热力 ---------- */
.radar-wrap{display:flex;align-items:center;gap:24px;flex-wrap:wrap}
.heat{display:grid;grid-template-columns:repeat(5,1fr);gap:6px}
.heat .d{aspect-ratio:1;border-radius:6px;background:rgba(255,255,255,.06)}
.heat .d.h1{background:rgba(76,141,255,.25)}
.heat .d.h2{background:rgba(76,141,255,.5)}
.heat .d.h3{background:rgba(76,141,255,.75)}
.heat .d.h4{background:var(--brand)}

/* ---------- Toast / 弹窗 ---------- */
#toast-wrap{position:fixed;top:18px;right:18px;z-index:999;display:flex;flex-direction:column;gap:10px}
.toast{background:var(--panel-solid);border:1px solid var(--line2);border-left:3px solid var(--brand);border-radius:12px;padding:12px 18px;font-size:13px;box-shadow:var(--shadow);min-width:220px;max-width:340px;animation:slideIn .25s}
.toast.ok{border-left-color:var(--ok)}
.toast.warn{border-left-color:var(--warn)}
.toast.bad{border-left-color:var(--bad)}
@keyframes slideIn{from{opacity:0;transform:translateX(20px)}to{opacity:1;transform:none}}
.modal-mask{position:fixed;inset:0;background:rgba(5,8,18,.72);display:grid;place-items:center;z-index:900;padding:20px}
.modal{background:var(--panel-solid);border:1px solid var(--line2);border-radius:18px;max-width:460px;width:100%;padding:24px;box-shadow:var(--shadow)}
.modal h3{font-size:17px;margin-bottom:12px}
.modal .actions{display:flex;gap:10px;justify-content:flex-end;margin-top:20px}

/* ---------- 移动端 ---------- */
.mobile-tab{display:none}
@media(max-width:980px){
  .sidebar{display:none}
  .mobile-tab{position:fixed;bottom:0;left:0;right:0;display:flex;background:rgba(10,15,30,.96);border-top:1px solid var(--line);z-index:100}
  .mobile-tab button{flex:1;background:none;border:none;color:var(--muted);padding:10px 4px;font-size:11px;display:flex;flex-direction:column;align-items:center;gap:3px}
  .mobile-tab button.active{color:var(--brand)}
  .mobile-tab .mi{font-size:18px}
  .view{padding:20px 16px 80px}
  .grid-2,.grid-3,.grid-4{grid-template-columns:1fr 1fr}
  .grid-3{grid-template-columns:1fr}
  .landing-hero h1{font-size:32px}
}
@media(max-width:560px){
  .grid-2,.grid-4{grid-template-columns:1fr}
  .opt-grid{grid-template-columns:1fr}
  .topbar{padding:12px 16px}
  .landing-hero{padding:40px 12px 24px}
}