:root {
  --bg:#0f0e0d; --surface:#1a1917; --surface2:#242220; --surface3:#2e2b28;
  --border:#333130; --border2:#403d3a;
  --text:#f0ede8; --muted:#8a8680; --hint:#5a5754;
  --green:#3ecf8e; --green-bg:rgba(62,207,142,0.1); --green-dim:#1a6647;
  --blue:#60a5fa; --blue-bg:rgba(96,165,250,0.1);
  --amber:#fbbf24; --amber-bg:rgba(251,191,36,0.1);
  --red:#f87171; --red-bg:rgba(248,113,113,0.1);
  --purple:#c084fc; --purple-bg:rgba(192,132,252,0.1);
  --teal:#2dd4bf; --teal-bg:rgba(45,212,191,0.1);
  --r:10px; --rl:16px;
  --chunk-a:#fbbf24; --chunk-b:#c084fc; --chunk-c:#60a5fa; --chunk-d:#3ecf8e;
}
*{box-sizing:border-box;margin:0;padding:0;}
html,body{height:100%;font-family:'Sora',sans-serif;background:var(--bg);color:var(--text);font-size:14px;line-height:1.6;}
::-webkit-scrollbar{width:4px;height:4px;}
::-webkit-scrollbar-track{background:transparent;}
::-webkit-scrollbar-thumb{background:var(--border2);border-radius:99px;}

/* === LAYOUT === */
.app{display:grid;grid-template-columns:240px 1fr;grid-template-rows:100vh;overflow:hidden;}
.sidebar{background:var(--surface);border-right:1px solid var(--border);display:flex;flex-direction:column;overflow:hidden;}
.main{display:flex;flex-direction:column;overflow:hidden;position:relative;}

/* === SIDEBAR === */
.sb-brand{padding:18px 16px 14px;border-bottom:1px solid var(--border);flex-shrink:0;}
.sb-logo{display:flex;align-items:center;gap:8px;}
.sb-logo-icon{width:28px;height:28px;background:var(--green);border-radius:7px;display:flex;align-items:center;justify-content:center;font-size:14px;flex-shrink:0;}
.sb-logo-text{font-size:15px;font-weight:700;letter-spacing:-0.3px;}
.sb-tagline{font-size:10px;color:var(--hint);margin-top:2px;letter-spacing:0.03em;}

.sb-nav{padding:8px 8px 4px;flex-shrink:0;}
.nav-btn{display:flex;align-items:center;gap:9px;width:100%;padding:8px 10px;border:none;background:none;color:var(--muted);font-family:'Sora',sans-serif;font-size:13px;cursor:pointer;border-radius:8px;transition:all .15s;text-align:left;}
.nav-btn:hover{background:var(--surface2);color:var(--text);}
.nav-btn.active{background:var(--surface3);color:var(--text);font-weight:500;}
.nav-icon{font-size:15px;width:18px;text-align:center;flex-shrink:0;}
.nav-badge{margin-left:auto;font-size:10px;font-weight:600;padding:2px 7px;border-radius:99px;background:var(--green-bg);color:var(--green);}

.sb-section{padding:14px 14px 4px;font-size:10px;font-weight:600;letter-spacing:.08em;color:var(--hint);text-transform:uppercase;flex-shrink:0;}
.sb-files{flex:1;overflow-y:auto;padding:4px 8px;}
.file-item{display:flex;align-items:center;gap:8px;padding:8px 10px;border-radius:8px;cursor:pointer;transition:all .15s;margin-bottom:2px;position:relative;}
.file-item:hover{background:var(--surface2);}
.file-item.active{background:var(--surface3);}
.fi-icon{font-size:16px;flex-shrink:0;}
.fi-info{flex:1;min-width:0;}
.fi-name{font-size:12px;font-weight:500;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;}
.fi-meta{font-size:10px;color:var(--hint);}
.fi-del{background:none;border:none;color:transparent;cursor:pointer;font-size:12px;padding:2px 4px;border-radius:4px;transition:all .15s;flex-shrink:0;}
.file-item:hover .fi-del{color:var(--hint);}
.fi-del:hover{color:var(--red)!important;background:var(--red-bg);}

.drop-zone{margin:8px;border:1.5px dashed var(--border);border-radius:var(--rl);padding:14px 10px;text-align:center;cursor:pointer;transition:all .2s;color:var(--hint);font-size:12px;flex-shrink:0;}
.drop-zone:hover,.drop-zone.drag{border-color:var(--green);background:var(--green-bg);color:var(--green);}
.dz-icon{font-size:20px;margin-bottom:4px;}

.sb-stats{padding:12px 14px;border-top:1px solid var(--border);display:grid;grid-template-columns:1fr 1fr;gap:8px;flex-shrink:0;}
.stat-m{text-align:center;background:var(--surface2);border-radius:8px;padding:8px 6px;}
.stat-m .n{font-size:17px;font-weight:700;color:var(--text);}
.stat-m .l{font-size:10px;color:var(--hint);margin-top:1px;}

/* === TOPBAR === */
.topbar{background:var(--surface);border-bottom:1px solid var(--border);padding:10px 20px;display:flex;align-items:center;gap:10px;flex-shrink:0;}
.tb-title{font-size:14px;font-weight:500;flex:1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;}
.mode-tabs{display:flex;gap:2px;background:var(--surface2);border-radius:8px;padding:2px;}
.mode-tab{font-size:12px;font-weight:500;padding:5px 11px;border-radius:6px;border:none;background:none;color:var(--muted);cursor:pointer;transition:all .15s;font-family:'Sora',sans-serif;}
.mode-tab.active{background:var(--surface3);color:var(--text);}
.menu-btn{display:none;background:var(--surface2);border:1px solid var(--border);color:var(--text);width:34px;height:34px;border-radius:8px;font-size:16px;line-height:1;cursor:pointer;align-items:center;justify-content:center;flex-shrink:0;}
.sb-backdrop{display:none;}

/* === CONTENT === */
.content{flex:1;overflow-y:auto;position:relative;}

/* === YOUTUBE PLAYER PANEL === */
.player-panel{background:var(--surface);border-bottom:1px solid var(--border);flex-shrink:0;}
.player-inner{display:flex;flex-direction:column;}
.yt-frame-wrap{position:relative;width:100%;background:#000;overflow:hidden;}
.yt-frame-wrap iframe{display:block;width:100%;height:100%;}
.player-controls{padding:10px 16px;display:flex;align-items:center;gap:10px;border-top:1px solid var(--border);}
.player-url-bar{display:flex;gap:6px;align-items:center;flex:1;}
.yt-input{flex:1;background:var(--surface2);border:1px solid var(--border);color:var(--text);font-family:'Sora',sans-serif;font-size:12px;padding:7px 12px;border-radius:8px;outline:none;transition:border-color .15s;}
.yt-input:focus{border-color:var(--green);}
.yt-input::placeholder{color:var(--hint);}
.btn-sm{font-size:11px;font-weight:600;padding:7px 14px;border-radius:8px;border:none;cursor:pointer;font-family:'Sora',sans-serif;transition:all .15s;white-space:nowrap;}
.btn-green{background:var(--green);color:#0f0e0d;}
.btn-green:hover{opacity:.85;}
.btn-ghost{background:var(--surface2);color:var(--muted);border:1px solid var(--border);}
.btn-ghost:hover{color:var(--text);background:var(--surface3);}
.btn-primary-lg{background:var(--green);color:#0f0e0d;font-size:13px;font-weight:600;padding:10px 22px;border-radius:99px;border:none;cursor:pointer;font-family:'Sora',sans-serif;transition:opacity .15s;}
.btn-primary-lg:hover{opacity:.85;}
.btn-outline{background:none;color:var(--muted);font-size:13px;padding:10px 18px;border-radius:99px;border:1px solid var(--border);cursor:pointer;font-family:'Sora',sans-serif;transition:all .15s;}
.btn-outline:hover{color:var(--text);border-color:var(--border2);}

.player-time{font-family:'JetBrains Mono',monospace;font-size:12px;color:var(--muted);}
.sync-badge{font-size:11px;padding:4px 10px;background:var(--green-bg);color:var(--green);border-radius:99px;font-weight:500;}
.nosync-badge{font-size:11px;padding:4px 10px;background:var(--amber-bg);color:var(--amber);border-radius:99px;font-weight:500;}

/* === TRANSCRIPT PANEL === */
.transcript-panel{flex:1;overflow-y:auto;padding:16px 20px;}
.lesson-hdr{margin-bottom:14px;}
.lesson-meta{font-size:11px;color:var(--hint);font-weight:600;letter-spacing:.06em;text-transform:uppercase;margin-bottom:4px;}
.lesson-title-big{font-size:17px;font-weight:600;letter-spacing:-.3px;margin-bottom:8px;}
.prog-bar{height:3px;background:var(--surface3);border-radius:99px;margin-bottom:6px;}
.prog-fill{height:3px;background:var(--green);border-radius:99px;transition:width .4s;}
.prog-label{font-size:11px;color:var(--hint);}

.lesson-dots{display:flex;flex-wrap:wrap;gap:5px;margin-bottom:14px;}
.ldot{width:28px;height:28px;border-radius:50%;border:1.5px solid var(--border);font-size:11px;font-weight:500;cursor:pointer;transition:all .2s;background:none;color:var(--hint);font-family:'Sora',sans-serif;}
.ldot.active{border-color:var(--text);background:var(--text);color:var(--bg);}
.ldot.done{border-color:var(--green);color:var(--green);background:var(--green-bg);}

/* === SENTENCE CARD === */
.sentence-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--rl);padding:14px 16px;margin-bottom:8px;transition:all .2s;position:relative;}
.sentence-card:hover{border-color:var(--border2);}
.sentence-card.active-card{border-color:var(--green);background:rgba(62,207,142,0.04);}
.sentence-card.shadowed{border-color:var(--green-dim);background:var(--green-bg);}
.sc-top{display:flex;align-items:flex-start;gap:10px;}
.sc-num{font-size:11px;color:var(--hint);font-family:'JetBrains Mono',monospace;padding-top:3px;flex-shrink:0;min-width:28px;}
.sc-body{flex:1;min-width:0;}
.sc-en{font-size:16px;line-height:1.7;color:var(--text);font-weight:400;}
.sc-vi{font-size:13px;color:var(--muted);margin-top:5px;padding-top:5px;border-top:1px solid var(--border);display:none;line-height:1.6;}
.sc-vi.show{display:block;}
.sc-vi-loading{color:var(--hint);font-style:italic;}
.sc-actions{display:flex;align-items:center;gap:5px;margin-top:8px;flex-wrap:wrap;}
.sc-btn{font-size:11px;padding:4px 10px;border-radius:99px;border:1px solid var(--border);background:none;color:var(--muted);cursor:pointer;transition:all .15s;font-family:'Sora',sans-serif;}
.sc-btn:hover{background:var(--surface2);color:var(--text);border-color:var(--border2);}
.sc-btn.active-vi{background:var(--blue-bg);color:var(--blue);border-color:rgba(96,165,250,.3);}
.sc-btn.done-btn{background:var(--green-bg);color:var(--green);border-color:var(--green-dim);}
.sc-btn.play-btn{background:var(--amber-bg);color:var(--amber);border-color:rgba(251,191,36,.3);}
.sc-btn.play-btn:hover{opacity:.8;}
.sc-timestamp{font-size:10px;color:var(--hint);font-family:'JetBrains Mono',monospace;margin-left:auto;}

/* === CHUNK HIGHLIGHTING === */
.chunk{border-radius:4px;padding:1px 0;cursor:pointer;position:relative;transition:all .15s;}
.chunk:hover{opacity:.8;}
.chunk-v{background:rgba(251,191,36,.18);border-bottom:2px solid var(--chunk-a);color:var(--chunk-a);}
.chunk-n{background:rgba(192,132,252,.15);border-bottom:2px solid var(--chunk-b);color:var(--chunk-b);}
.chunk-p{background:rgba(96,165,250,.15);border-bottom:2px solid var(--chunk-c);color:var(--chunk-c);}
.chunk-a{background:rgba(62,207,142,.15);border-bottom:2px solid var(--chunk-d);color:var(--chunk-d);}
.word-b2{border-bottom:1px dashed var(--hint);cursor:pointer;}
.word-b2:hover{color:var(--blue);}

/* === CHUNK LEGEND === */
.chunk-legend{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:12px;background:var(--surface);border:1px solid var(--border);border-radius:var(--r);padding:8px 12px;}
.cl-item{display:flex;align-items:center;gap:5px;font-size:11px;color:var(--muted);}
.cl-dot{width:10px;height:10px;border-radius:2px;}

/* === TOOLTIP === */
.tooltip-box{position:fixed;background:var(--surface3);border:1px solid var(--border2);color:var(--text);font-size:12px;padding:8px 13px;border-radius:10px;pointer-events:none;z-index:9999;max-width:260px;line-height:1.5;box-shadow:0 8px 24px rgba(0,0,0,.5);display:none;}
.tt-word{font-weight:600;color:var(--green);font-size:13px;margin-bottom:2px;}
.tt-type{font-size:10px;color:var(--hint);margin-bottom:4px;text-transform:uppercase;letter-spacing:.04em;}
.tt-meaning{color:var(--text);}

/* === WORD KARAOKE + DICTIONARY POPUP === */
.sc-en .w{cursor:pointer;border-radius:3px;padding:0 1px;transition:background .1s,color .1s;}
.sc-en .w:hover{background:var(--surface2);}
.sc-en .w.w-active{background:var(--amber);color:#15151b;font-weight:600;}
.sc-en .w.w-done{color:var(--muted);}

.dict-pop{position:fixed;z-index:10001;width:340px;max-width:calc(100vw - 16px);background:var(--surface);border:1px solid var(--border2);border-radius:12px;box-shadow:0 12px 36px rgba(0,0,0,.6);overflow:hidden;font-size:13px;}
.dict-head{display:flex;align-items:center;gap:8px;padding:12px 14px 8px;}
.dict-word{font-weight:700;font-size:18px;color:var(--text);}
.dict-ipa{font-family:'JetBrains Mono',monospace;font-size:12px;color:var(--green);}
.dict-audio,.dict-close{background:none;border:none;color:var(--muted);cursor:pointer;font-size:15px;line-height:1;padding:4px;border-radius:6px;}
.dict-audio:hover,.dict-close:hover{background:var(--surface2);color:var(--text);}
.dict-close{margin-left:auto;}
.dict-tabs{display:flex;gap:2px;padding:0 10px;background:var(--surface2);}
.dict-tab{flex:1;background:none;border:none;color:var(--muted);cursor:pointer;font-family:'Sora',sans-serif;font-size:12px;padding:8px 6px;border-bottom:2px solid transparent;}
.dict-tab.active{color:var(--text);border-bottom-color:var(--green);font-weight:600;}
.dict-body{padding:12px 14px;max-height:46vh;overflow:auto;line-height:1.55;}
.dp-loading,.dp-empty{color:var(--hint);font-style:italic;}
.dp-pos{font-size:10px;text-transform:uppercase;letter-spacing:.04em;color:var(--blue);margin:6px 0 2px;}
.dp-defs{margin:0;padding-left:18px;color:var(--text);}
.dp-defs li{margin-bottom:5px;}
.dp-ex{color:var(--muted);font-style:italic;margin-top:2px;}
.dp-vi{color:var(--text);font-size:15px;}
@media(max-width:520px){
  .dict-pop.sheet{left:0!important;right:0;bottom:0;top:auto!important;width:100%;max-width:100%;border-radius:14px 14px 0 0;}
  .dict-pop.sheet .dict-body{max-height:40vh;}
}

/* === CHUNK PANEL (sidebar detail) === */
.chunk-panel{margin-top:12px;background:var(--surface);border:1px solid var(--border);border-radius:var(--rl);overflow:hidden;}
.cp-header{padding:10px 14px;border-bottom:1px solid var(--border);font-size:12px;font-weight:600;color:var(--muted);text-transform:uppercase;letter-spacing:.06em;}
.cp-body{padding:10px 14px;display:flex;flex-direction:column;gap:6px;}
.chunk-item{display:flex;align-items:flex-start;gap:10px;padding:8px 10px;border-radius:8px;background:var(--surface2);cursor:pointer;transition:all .15s;}
.chunk-item:hover{background:var(--surface3);}
.ci-badge{font-size:10px;font-weight:700;padding:3px 8px;border-radius:99px;flex-shrink:0;margin-top:1px;}
.ci-badge.v{background:var(--amber-bg);color:var(--amber);}
.ci-badge.n{background:var(--purple-bg);color:var(--purple);}
.ci-badge.p{background:var(--blue-bg);color:var(--blue);}
.ci-badge.a{background:var(--green-bg);color:var(--green);}
.ci-content{flex:1;min-width:0;}
.ci-phrase{font-size:13px;font-weight:500;margin-bottom:1px;}
.ci-vi{font-size:12px;color:var(--muted);}
.ci-level{font-size:10px;color:var(--hint);margin-top:1px;}

/* === FILL MODE === */
.fill-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--rl);padding:14px 18px;margin-bottom:10px;}
.fill-head{display:flex;align-items:center;gap:8px;margin-bottom:8px;}
.fill-tag{font-size:11px;color:var(--hint);min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;}
.fill-sentence{font-size:15px;line-height:2.2;color:var(--text);}
.fill-input{border:none;border-bottom:2px solid var(--green-dim);background:transparent;color:var(--text);font-size:15px;font-family:'Sora',sans-serif;padding:0 6px;outline:none;min-width:90px;text-align:center;transition:all .2s;}
.fill-input:focus{border-bottom-color:var(--green);}
.fill-input.ok{border-bottom-color:var(--green);color:var(--green);}
.fill-input.err{border-bottom-color:var(--red);color:var(--red);}
.fill-result{padding:10px 14px;border-radius:var(--r);font-size:13px;margin-top:12px;display:none;}
.fill-result.ok{background:var(--green-bg);color:var(--green);display:block;}
.fill-result.err{background:var(--red-bg);color:var(--red);display:block;}

/* === VOCAB MODE === */
.vocab-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(180px,1fr));gap:8px;}
.vc{background:var(--surface);border:1px solid var(--border);border-radius:var(--r);padding:12px 14px;cursor:pointer;transition:all .2s;}
.vc:hover{border-color:var(--border2);transform:translateY(-1px);}
.vc.flipped{background:var(--surface2);border-color:var(--border2);}
.vc-level{font-size:10px;font-weight:700;padding:2px 7px;border-radius:99px;display:inline-block;margin-bottom:6px;}
.lv-b2{background:var(--blue-bg);color:var(--blue);}
.lv-c1{background:var(--purple-bg);color:var(--purple);}
.lv-c2{background:var(--amber-bg);color:var(--amber);}
.vc-word{font-size:14px;font-weight:600;margin-bottom:2px;}
.vc-type{font-size:11px;color:var(--hint);}
.vc-vi{font-size:12px;color:var(--muted);margin-top:6px;display:none;padding-top:6px;border-top:1px solid var(--border);}
.vc-vi.show{display:block;}

/* === QUIZ === */
.quiz-wrap{max-width:580px;margin:0 auto;padding:20px;}
.quiz-prog-row{display:flex;align-items:center;gap:10px;margin-bottom:16px;}
.quiz-score-badge{font-size:12px;font-weight:600;padding:4px 12px;background:var(--surface2);border-radius:99px;color:var(--muted);}
.quiz-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--rl);padding:24px;margin-bottom:12px;}
.quiz-type{font-size:10px;font-weight:700;text-transform:uppercase;letter-spacing:.06em;margin-bottom:8px;}
.quiz-q{font-size:16px;font-weight:500;margin-bottom:6px;line-height:1.5;}
.quiz-ctx{font-size:13px;color:var(--muted);font-style:italic;margin-bottom:18px;padding:8px 12px;background:var(--surface2);border-radius:8px;border-left:3px solid var(--border2);}
.quiz-opts{display:flex;flex-direction:column;gap:7px;}
.quiz-opt{padding:12px 16px;border-radius:var(--r);border:1.5px solid var(--border);font-size:14px;cursor:pointer;background:none;font-family:'Sora',sans-serif;text-align:left;color:var(--text);transition:all .15s;}
.quiz-opt:hover:not(:disabled){border-color:var(--border2);background:var(--surface2);}
.quiz-opt.ok{border-color:var(--green);background:var(--green-bg);color:var(--green);}
.quiz-opt.err{border-color:var(--red);background:var(--red-bg);color:var(--red);}
.quiz-exp{font-size:13px;color:var(--muted);margin-top:12px;padding:10px 14px;background:var(--surface2);border-radius:8px;display:none;border-left:3px solid var(--border2);}
.quiz-exp.show{display:block;}
.quiz-next{margin-top:14px;padding:9px 22px;background:var(--green);color:#0f0e0d;border:none;border-radius:99px;font-size:13px;font-weight:600;cursor:pointer;display:none;font-family:'Sora',sans-serif;}
.quiz-next.show{display:inline-block;}
.quiz-done{text-align:center;padding:50px 20px;}

/* === SETTINGS === */
.settings-wrap{max-width:520px;margin:0 auto;padding:20px;}
.settings-card{background:var(--surface);border:1px solid var(--border);border-radius:var(--rl);padding:18px 20px;margin-bottom:12px;}
.sc-title{font-size:13px;font-weight:600;margin-bottom:14px;color:var(--text);}
.sr{display:flex;align-items:center;justify-content:space-between;padding:9px 0;border-bottom:1px solid var(--border);font-size:13px;}
.sr:last-child{border-bottom:none;}
.sr-label{color:var(--muted);}
.toggle{position:relative;width:38px;height:20px;flex-shrink:0;}
.toggle input{opacity:0;width:0;height:0;}
.tsl{position:absolute;inset:0;background:var(--surface3);border-radius:99px;cursor:pointer;transition:.2s;}
.tsl:before{content:'';position:absolute;width:14px;height:14px;left:3px;top:3px;background:var(--hint);border-radius:50%;transition:.2s;}
.toggle input:checked+.tsl{background:var(--green);}
.toggle input:checked+.tsl:before{transform:translateX(18px);background:#0f0e0d;}
select.s-sel{font-size:12px;padding:5px 10px;border:1px solid var(--border);border-radius:7px;background:var(--surface2);color:var(--text);font-family:'Sora',sans-serif;cursor:pointer;outline:none;}

/* === WELCOME === */
.welcome{max-width:540px;margin:50px auto;text-align:center;padding:0 20px;}
.wl-icon{font-size:48px;margin-bottom:18px;}
.wl-title{font-size:24px;font-weight:700;letter-spacing:-.5px;margin-bottom:8px;}
.wl-sub{color:var(--muted);font-size:14px;line-height:1.8;margin-bottom:28px;}
.wl-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-bottom:28px;text-align:left;}
.wl-step{background:var(--surface);border:1px solid var(--border);border-radius:var(--rl);padding:14px;}
.wl-step-n{font-size:10px;font-weight:700;color:var(--hint);text-transform:uppercase;letter-spacing:.06em;margin-bottom:5px;}
.wl-step-t{font-size:13px;font-weight:500;margin-bottom:2px;}
.wl-step-s{font-size:11px;color:var(--hint);}

/* === EMPTY STATE === */
.empty{text-align:center;padding:60px 20px;color:var(--hint);}
.empty .ei{font-size:38px;margin-bottom:12px;}
.empty p{font-size:13px;}

/* Animations */
@keyframes fadeUp{from{opacity:0;transform:translateY(10px)}to{opacity:1;transform:translateY(0)}}
.anim{animation:fadeUp .25s ease;}
@keyframes pulse{0%,100%{opacity:1}50%{opacity:.5}}
.pulsing{animation:pulse 1.5s infinite;}

/* === SCROLLABLE TRANSCRIPT LAYOUT === */
.study-layout{display:flex;flex-direction:column;height:100%;}
.player-area{flex-shrink:0;}
.transcript-area{flex:1;overflow-y:auto;padding:14px 18px;}

/* === RESPONSIVE === */
/* Điện thoại + iPad dọc (≤820px): sidebar thành ngăn kéo trượt */
@media(max-width:820px){
  .app{grid-template-columns:1fr;}
  .menu-btn{display:flex;}
  .sidebar{
    position:fixed;top:0;left:0;bottom:0;width:82%;max-width:300px;max-height:none;
    z-index:60;transform:translateX(-100%);transition:transform .25s ease;
    box-shadow:0 0 40px rgba(0,0,0,.5);
  }
  body.sidebar-open .sidebar{transform:none;}
  .sb-backdrop{
    display:block;position:fixed;inset:0;background:rgba(0,0,0,.55);z-index:55;
    opacity:0;visibility:hidden;transition:opacity .25s,visibility .25s;
  }
  body.sidebar-open .sb-backdrop{opacity:1;visibility:visible;}

  .topbar{padding:8px 12px;gap:8px;}
  .mode-tab{padding:6px 9px;}
  .transcript-area{padding:12px 12px;}
  .transcript-panel{padding:14px 12px;}
  .player-controls{flex-wrap:wrap;padding:10px 12px;gap:8px;}
  .player-url-bar{flex-basis:100%;}
  .wl-grid{grid-template-columns:1fr;}
  .welcome{margin:30px auto;}
  .vocab-grid{grid-template-columns:repeat(auto-fill,minmax(150px,1fr));}
  .quiz-wrap,.settings-wrap{padding:14px 12px;}
  .sentence-card{padding:12px 14px;}
  .sc-en{font-size:15px;}
  .sc-btn{padding:6px 12px;font-size:12px;}
  .ldot{width:32px;height:32px;}
}
/* Điện thoại nhỏ (≤430px) */
@media(max-width:430px){
  .sc-en{font-size:14px;line-height:1.6;}
  .lesson-title-big{font-size:16px;}
  .mode-tab{padding:6px 8px;font-size:11px;}
  .vocab-grid{grid-template-columns:1fr 1fr;}
  .quiz-q{font-size:15px;}
  .quiz-card{padding:18px 16px;}
  .btn-primary-lg,.btn-outline{padding:9px 16px;font-size:13px;}
  .sb-stats{grid-template-columns:1fr 1fr;}
}