:root{
      --bg: #0b1020;
      --panel: rgba(255,255,255,0.06);
      --panel-strong: rgba(255,255,255,0.12);
      --text: #e8ecf3;
      --muted: #b5c0d0;
      --border: rgba(255,255,255,0.12);
      --primary: #7c5cff;
      --primary-2: #19d3c5;
      --success: #43d39e;
      --danger: #ff5d70;
      --warning: #ffb14a;
      --shadow: 0 10px 30px rgba(0,0,0,0.35);
      --radius-lg: 16px;
      --radius: 12px;
      --glass: blur(10px) saturate(140%);
      --focus: 0 0 0 3px rgba(124,92,255,.35);
      --font: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji","Segoe UI Emoji";
    }
    [data-theme="light"]{
      --bg: #f6f8ff;
      --panel: rgba(255,255,255,0.85);
      --panel-strong: rgba(255,255,255,1);
      --text: #101426;
      --muted: #5d667b;
      --border: rgba(8,15,35,0.08);
      --shadow: 0 10px 30px rgba(40,48,80,0.12);
    }
    *{box-sizing:border-box}
    html,body{height:100%}
    body{
      margin:0; color:var(--text); font-family:var(--font);
      background:
        radial-gradient(1200px 800px at 110% -10%, rgba(124,92,255,0.35), transparent 60%),
        radial-gradient(1000px 700px at -10% 110%, rgba(25,211,197,0.35), transparent 60%),
        var(--bg);
      background-attachment: fixed; line-height:1.45;
    }
    a{color:inherit;text-decoration:none}
    button{font:inherit;color:inherit}
    .app{display:grid; grid-template-columns: 280px 1fr; min-height:100vh;}

    /* Sidebar */
    .sidebar{
      position:sticky; top:0; height:100vh; align-self:start;
      backdrop-filter: var(--glass);
      background: linear-gradient(180deg, rgba(255,255,255,0.04), rgba(255,255,255,0.02));
      border-right:1px solid var(--border);
      padding:16px; display:flex; flex-direction:column; gap:16px;
    }
    .brand{display:flex; align-items:center; gap:12px; padding:10px 12px; border-radius:14px; background:var(--panel); box-shadow: var(--shadow); cursor: pointer; transition: 0.2s;}
    .brand:hover { transform: scale(1.02); }
    .brand h1{font-size:18px; line-height:1.2; margin:0}
    .badge{font-size:11px; background:linear-gradient(135deg,var(--primary),var(--primary-2)); color:#fff; padding:2px 8px; border-radius:999px; margin-left:auto;}
    .topic-list{overflow:auto; padding-right:6px;}
    .topic{
      display:flex; align-items:center; gap:10px; padding:10px 12px; margin-bottom:8px;
      border-radius:12px; cursor:pointer; border:1px solid var(--border); background:var(--panel); transition:.2s ease;
    }
    .topic:hover{transform:translateY(-1px)}
    .topic.active{box-shadow: var(--focus); border-color: transparent; background:
      linear-gradient(135deg, rgba(124,92,255,0.18), rgba(25,211,197,0.18)), var(--panel-strong);}
    .topic .meta{margin-left:auto; font-size:12px; color:var(--muted)}
    .progress{height:6px; background:rgba(255,255,255,0.15); border-radius:8px; overflow:hidden; margin-top:6px;}
    .progress > span{display:block; height:100%; background: linear-gradient(90deg, var(--primary), var(--primary-2)); width:0%;}
    .sidebar-actions{margin-top:auto; display:flex; gap:8px; flex-wrap:wrap;}
    .btn{
      border:1px solid var(--border); background:var(--panel-strong); color:inherit;
      padding:10px 12px; border-radius:10px; cursor:pointer; display:inline-flex; align-items:center; gap:8px;
      transition:.2s ease; box-shadow: 0 1px 0 rgba(0,0,0,0.02);
    }
    .btn:hover{transform:translateY(-1px)}
    .btn.primary{background: linear-gradient(135deg,var(--primary),var(--primary-2)); color:#fff; border:0;}
    .btn.small{padding:8px 10px; border-radius:8px; font-size:13px}
    .btn.icon{padding:8px; border-radius:10px; width:38px; height:38px; display:inline-grid; place-items:center;}
    .btn.danger{background: rgba(255,93,112,0.12); border-color: rgba(255,93,112,0.25); color:#ff5d70;}

    /* Main */
    .main{display:grid; grid-template-rows: auto 1fr; min-width:0;}
    .topbar{
      position:sticky; top:0; z-index:10; display:flex; align-items:center; gap:12px; padding:14px 18px;
      background: linear-gradient(180deg, rgba(255,255,255,0.85), rgba(255,255,255,0.65));
      backdrop-filter: var(--glass); border-bottom:1px solid var(--border);
    }
    [data-theme="dark"] .topbar{background: linear-gradient(180deg, rgba(10,12,26,0.7), rgba(10,12,26,0.45));}
    .hamburger{display:none}
    .search{flex:1; display:flex; align-items:center; gap:10px; background:var(--panel-strong); border:1px solid var(--border); border-radius:12px; padding:10px 12px;}
    .search input{border:0; outline:0; background:transparent; color:inherit; width:100%;}
    .tabs{display:flex; gap:8px; margin-left:auto;}
    .tab-btn{padding:10px 12px; border-radius:10px; border:1px solid var(--border); background:var(--panel-strong); cursor:pointer;}
    .tab-btn.active{background: linear-gradient(135deg,var(--primary),var(--primary-2)); border-color:transparent; color:#fff;}
    .content{padding:20px; min-width:0; overflow:auto; display:grid; gap:20px; grid-template-columns: 1fr;}
    .section{background:var(--panel-strong); border:1px solid var(--border); border-radius:var(--radius-lg); padding:16px; box-shadow: var(--shadow);}
    .section-header{display:flex; align-items:center; justify-content:space-between; gap:12px; margin-bottom:12px;}
    .section-title{font-size:18px; margin:0}

    /* Flashcard (reveal on flip) */
    .flashcard{
      background: radial-gradient(120% 120% at 0% 0%, rgba(124,92,255,0.18), transparent 40%),
                  radial-gradient(120% 120% at 100% 100%, rgba(25,211,197,0.18), transparent 40%),
                  var(--panel-strong);
      border:1px solid var(--border); border-radius:18px; box-shadow: var(--shadow);
      padding:14px; min-height:340px; display:flex; flex-direction:column; gap:12px;
    }
    .hero{display:flex; align-items:flex-end; gap:10px; padding:4px 4px 0 4px; flex-wrap:wrap}
    .pos{font-size:12px; color:var(--muted); border:1px dashed var(--border); padding:2px 8px; border-radius:999px}
    .word{font-size:34px; font-weight:800; letter-spacing:.3px;}
    .ipa{font-size:18px; color:var(--muted); margin-left:4px}
    .hint-box{
      display:grid; place-items:center; color:var(--muted); font-size:14px;
      border:1px dashed var(--border); border-radius:12px; padding:14px; background:var(--panel);
      min-height:80px;
    }
    .details{display:none; gap:10px;}
    .details.show{display:grid;}
    .media{
      position:relative; aspect-ratio: 16/9; width:95%;height: 400px;
      background:var(--panel); border:1px dashed var(--border); border-radius:12px; overflow:hidden;
      display:grid; place-items:center;
    }
    .media img{width:90%; height:70%; object-fit:cover; display:none;}
    .media .placeholder{width:70%; height:60%; display:grid; place-items:center; color:var(--muted); font-weight:500; font-size:48px;}
    .trans{font-size:20px;}
    .example{font-size:20px; color:var(--muted); background:var(--panel); border:1px dashed var(--border); padding:8px 10px; border-radius:10px;}
    /* Translation row with audio button */
    .trans-row{display:flex; align-items:center; gap:8px;}
    .trans-row .trans{flex:1}

    /* Action bar under card */
    .flash-actions{
      margin-top:14px; display:flex; flex-wrap:wrap; gap:12px; justify-content:center;
    }
    .pill{
      font-size:14px; padding:12px 16px; border-radius:999px; border:1px solid var(--border);
      background:var(--panel-strong); cursor:pointer;
    }
    .pill.primary{background: rgba(255,177,74,0.12); border-color: rgba(255,177,74,0.25); color:#cc7b11}
    .pill.success{background: rgba(67,211,158,0.12); border-color: rgba(67,211,158,0.25); color:#2fbf8f}
    .pill.danger{background: rgba(255,93,112,0.12); border-color: rgba(255,93,112,0.25); color:#ff5d70}

    /* Quiz */
    .quiz{display:grid; gap:14px;}
    .question{background:var(--panel); border:1px dashed var(--border); padding:12px; border-radius:12px;}
    .answers{display:grid; gap:10px}
    .answer{padding:12px; border-radius:10px; border:1px solid var(--border); background:var(--panel-strong); cursor:pointer; display:flex; gap:8px; align-items:center;}
    .answer.correct{border-color: rgba(67,211,158,0.45); background:rgba(67,211,158,0.12)}
    .answer.wrong{border-color: rgba(255,93,112,0.45); background:rgba(255,93,112,0.12)}
    .quiz-footer{display:flex; justify-content:space-between; align-items:center; gap:10px}
    .score{font-size:14px; color:var(--muted);}

    /* List */
    .list-controls{display:flex; gap:10px; flex-wrap:wrap; align-items:center; justify-content:space-between}
    .table{width:100%; border-collapse:separate; border-spacing:0 8px;}
    .table th{text-align:left; font-size:12px; color:var(--muted); font-weight:600; padding:6px 10px;}
    .table td{background:var(--panel-strong); border:1px solid var(--border); padding:12px 10px; vertical-align:top;}
    .table tr td:first-child{border-top-left-radius:10px;border-bottom-left-radius:10px}
    .table tr td:last-child{border-top-right-radius:10px;border-bottom-right-radius:10px}
    .star{cursor:pointer; color:#d0d6ff; opacity:.7; transition:.2s;}
    .star.active{color:#ffd54b; opacity:1}
    .chip{font-size:11px; padding:4px 8px; border-radius:999px; background:var(--panel); border:1px solid var(--border); color:var(--muted);}

    /* Footer */
    .footer{text-align:center; color:var(--muted); font-size:13px; padding:6px 0 12px;}

    /* Modal */
    .modal-backdrop{position:fixed; inset:0; background:rgba(0,0,0,0.5); display:none; align-items:center; justify-content:center; padding:16px; z-index:200;}
    .modal{width:min(920px, 100%); background:var(--panel-strong); border:1px solid var(--border); border-radius:16px; box-shadow: var(--shadow);
      max-height:90vh; overflow:auto; padding:16px;}
    .modal h3{margin:0 0 8px 0}
    .modal pre, .modal code{white-space:pre; overflow:auto; background:var(--panel); border:1px dashed var(--border); border-radius:10px; padding:10px; color:inherit;}
    .modal-actions{display:flex; gap:10px; flex-wrap:wrap; justify-content:flex-end; margin-top:10px}
    .modal-backdrop.show{display:flex}

    /* Mobile */
    @media (max-width: 900px){
      .app{grid-template-columns: 1fr}
      .sidebar{position:fixed; left:0; top:0; width:82%; max-width:360px; transform: translateX(-105%); height:100vh; z-index:100; transition:.3s ease; box-shadow: 20px 0 40px rgba(0,0,0,0.35);}
      .sidebar.show{transform:translateX(0)}
      .topbar{padding:12px}
      .hamburger{display:inline-flex}
      .content{padding:14px}
    }

    /* Utilities */
    .hidden{display:none !important}
    .spacer{flex:1}
    .hint{font-size:12px; color:var(--muted)}
    .mr-6{margin-right:6px}
    .btn:focus,.tab-btn:focus,.topic:focus,.answer:focus,.pill:focus{outline:none; box-shadow: var(--focus)}
    .switch{position:relative; display:inline-block; width:44px; height:24px; vertical-align:middle}
    .switch input{display:none}
    .switch span{position:absolute; cursor:pointer; top:0; left:0; right:0; bottom:0; background:#aab2c5; border-radius:999px; transition:.2s}
    .switch span:before{content:""; position:absolute; height:18px; width:18px; left:3px; top:3px; background:white; border-radius:50%; transition:.2s}
    .switch input:checked + span{background:#7c5cff}
    .switch input:checked + span:before{transform:translateX(20px)}
	
	/* --- CSS MỚI THÊM VÀO --- */

	/* Khung chứa media đẹp hơn */
	.media {
	  background: var(--panel-strong); /* Nền tối hơn chút */
	  border: 1px solid var(--border);
	  box-shadow: inset 0 0 20px rgba(0,0,0,0.05);
	  position: relative;
	  overflow: hidden;
	}

	/* Ảnh hiển thị dạng cover đẹp mắt */
	.media img {
	  width: 100%;
	  height: 100%;
	  object-fit: contain; /* Đảm bảo nhìn thấy toàn bộ ảnh */
	  background: #000; /* Nền đen cho ảnh dọc/ngang không khớp */
	}

	/* Hiệu ứng hiện ảnh mượt mà */
	.fade-in-img {
	  animation: fadeInMedia 0.5s ease-out;
	}
	@keyframes fadeInMedia {
	  from { opacity: 0; transform: scale(0.95); }
	  to { opacity: 1; transform: scale(1); }
	}

	/* Hiệu ứng Skeleton Loading (Đang tải...) */
	.skeleton-loader {
	  width: 100%;
	  height: 100%;
	  background: linear-gradient(90deg, 
		  rgba(255,255,255,0) 0%, 
		  rgba(255,255,255,0.2) 50%, 
		  rgba(255,255,255,0) 100%);
	  background-size: 200% 100%;
	  animation: shimmer 1.5s infinite;
	}
	[data-theme="light"] .skeleton-loader {
	  background: linear-gradient(90deg, 
		  rgba(0,0,0,0) 0%, 
		  rgba(0,0,0,0.05) 50%, 
		  rgba(0,0,0,0) 100%);
	}
	@keyframes shimmer {
	  0% { background-position: -200% 0; }
	  100% { background-position: 200% 0; }
	}