:root {
    --bg-color: #0a0a0a;
    --card-bg: #161616;
    --text-main: #e0e0e0;
    --text-sub: #888888;
    --accent: #ffffff;
    --accent-hover: #cccccc;
    --border: #262626;
    --success: #4caf50;
    --error: #f44336;
    --btn-primary: #3b82f6; 
    --btn-primary-hover: #2563eb;
    --btn-youglish: #e62117; 
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --warning: #ff9800;
}

* {
    box-sizing: border-box;
    outline: none;
}

body {
    background-color: var(--bg-color);
    color: var(--text-main);
    font-family: var(--font-family);
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
}

.container {
    width: 100%;
    max-width: 600px;
    padding: 40px 20px;
    display: flex;
    flex-direction: column;
}

header {
    margin-bottom: 40px;
    text-align: center;
    letter-spacing: 2px;
    text-transform: uppercase;
}

h1 {
    font-size: 1.4rem;
    font-weight: 300;
    letter-spacing: 3px;
    margin: 0;
    color: var(--accent);
}

h2 {
    font-size: 1.1rem;
    font-weight: 400;
    margin-bottom: 20px;
    letter-spacing: 0.5px;
}

/* Navigation Bar */
.nav-bar {
    margin-bottom: 30px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    min-height: 40px;
}

.nav-bar-right {
    display: flex;
    align-items: center;
    justify-content: flex-end;
    gap: 12px;
    flex-shrink: 0;
    position: relative;
}

.btn-icon {
    background: none;
    border: none;
    color: var(--text-sub);
    cursor: pointer;
    font-size: 0.9rem;
    transition: color 0.2s;
    padding: 6px 12px;
    border: 1px solid var(--border);
    border-radius: 15px;
    letter-spacing: 0.5px;
}

.btn-icon:hover {
    color: var(--accent);
    border-color: var(--text-sub);
}

.export-quiz-btn { 
    font-size: 0.8rem; 
    border: 1px solid var(--text-sub); 
    color: var(--text-sub); 
    padding: 5px 14px; 
    border-radius: 20px; 
    background: transparent; 
    cursor: pointer; 
    white-space: nowrap !important; 
    display: inline-block !important; 
    visibility: visible !important;
    opacity: 1 !important;
    transition: all 0.2s;
    z-index: 10;
    letter-spacing: 0.5px;
}

.export-quiz-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
}

.card {
    background-color: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 24px;
    margin-bottom: 16px;
    transition: transform 0.2s, border-color 0.2s;
}

.book-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    padding: 18px;
    margin-bottom: 12px;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: var(--card-bg);
}

.book-item:hover {
    border-color: var(--text-sub);
}

.book-item.selected {
    border-color: var(--accent);
    background-color: #1c1c1c;
}

.word-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.95rem;
    padding: 14px 0;
    border-bottom: 1px solid #1f1f1f;
}

.word-item:last-child {
    border-bottom: none;
}

.word-en {
    font-weight: 500;
    color: var(--accent);
    letter-spacing: 0.5px;
}

.word-zh {
    color: var(--text-sub);
    font-size: 0.9rem;
    margin-top: 4px;
}

input[type="text"], input[type="number"], textarea {
    width: 100%;
    background: transparent;
    border: none;
    border-bottom: 1px solid var(--border);
    color: var(--text-main);
    padding: 12px 0;
    font-size: 1rem;
    margin-bottom: 24px;
    transition: border-color 0.2s;
    font-family: var(--font-family);
}

input[type="text"]:focus, input[type="number"]:focus, textarea:focus {
    border-bottom-color: var(--accent);
}

textarea {
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 12px;
    min-height: 120px;
    margin-top: 10px;
    font-size: 0.9rem;
    line-height: 1.6;
    resize: vertical;
}

.btn {
    background-color: var(--accent);
    color: var(--bg-color);
    border: none;
    padding: 14px 24px;
    border-radius: 30px;
    font-weight: 500;
    cursor: pointer;
    font-size: 0.9rem;
    width: 100%;
    margin-top: 10px;
    transition: background 0.2s;
    letter-spacing: 0.5px;
}

.btn:hover {
    background-color: var(--accent-hover);
}

.btn-outline {
    background: transparent;
    color: var(--text-main);
    border: 1px solid var(--border);
}

.btn-outline:hover {
    border-color: var(--accent);
}

.btn-small {
    padding: 6px 14px;
    font-size: 0.8rem;
    width: auto;
    margin: 0;
    border-radius: 15px;
}

.btn-delete {
    background: transparent;
    color: #666;
    border: 1px solid #333;
}

.btn-delete:hover {
    color: var(--error);
    border-color: var(--error);
    background: transparent;
}

.btn-yg {
    border-color: #444;
    color: var(--text-main);
}

.btn-yg:hover {
    background-color: var(--btn-youglish);
    border-color: var(--btn-youglish);
    color: white;
}

.practice-area {
    text-align: center;
    margin-top: 40px;
    position: relative;
}

.question-text {
    font-size: 1.8rem;
    margin-bottom: 35px;
    font-weight: 500;
    letter-spacing: 0.5px;
}

.hint-text {
    color: var(--text-sub);
    margin-bottom: 12px;
    font-style: italic;
    height: 20px;
    font-size: 0.9rem;
    letter-spacing: 1px;
}

.progress-text {
    color: var(--text-sub);
    margin-top: 25px;
    font-size: 0.8rem;
    letter-spacing: 0.5px;
}

#feedback-area, #mcq-feedback-area, #speaking-feedback-area, #mastery-feedback-area {
    display: none;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    animation: fadeIn 0.3s ease;
    width: 100%;
}

.big-icon {
    font-size: 3rem;
    margin-bottom: 15px;
    font-weight: 300;
}

.icon-correct { color: var(--success); }
.icon-wrong { color: var(--error); }

.result-status {
    font-size: 1.1rem;
    font-weight: 500;
    margin-bottom: 25px;
    letter-spacing: 0.5px;
}

.status-correct { color: var(--success); }
.status-wrong { color: var(--error); }

.result-msg {
    margin-top: 15px;
    font-size: 1rem;
    font-weight: 500;
    text-align: center;
    min-height: 30px;
    transition: color 0.2s;
    letter-spacing: 0.5px;
}
.result-correct { color: var(--success); }
.result-wrong { color: var(--error); }

.answer-reveal {
    font-size: 1.3rem;
    margin-bottom: 15px;
    color: var(--text-sub);
    display: flex;
    align-items: center;
    gap: 12px;
    justify-content: center;
}

.tts-btn-large {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text-sub);
    cursor: pointer;
    font-size: 0.85rem;
    transition: all 0.2s;
}

.tts-btn-large:hover {
    color: var(--accent);
    border-color: var(--text-sub);
}

.btn-next-big {
    background-color: var(--btn-primary);
    color: white;
    font-size: 1.05rem;
    padding: 14px;
    margin-top: 30px;
    border-radius: 8px;
    width: 100%;
}

.btn-next-big:hover {
    background-color: var(--btn-primary-hover);
}

.mcq-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
    margin-bottom: 20px;
}

.btn-mcq {
    background: var(--card-bg);
    border: 1px solid var(--border);
    color: var(--text-main);
    padding: 18px;
    border-radius: 12px;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.2s;
    word-break: break-all;
    letter-spacing: 0.5px;
}

.btn-mcq:hover {
    border-color: var(--text-sub);
    transform: translateY(-1px);
}

@media (max-width: 480px) {
    .mcq-grid { grid-template-columns: 1fr; }
}

/* ======= 雙向連接 (Match) Mode Styles ======= */
.match-container {
    display: flex;
    gap: 15px;
    justify-content: space-between;
    width: 100%;
    margin-top: 20px;
}

.match-col {
    display: flex;
    flex-direction: column;
    gap: 10px;
    width: 48%;
}

.match-btn {
    background: var(--card-bg);
    border: 1px solid var(--border);
    color: var(--text-main);
    padding: 14px 10px;
    border-radius: 8px;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.2s;
    word-break: break-all;
}

.match-btn:hover { border-color: var(--text-sub); }
.match-btn.selected { border-color: var(--btn-primary); background: rgba(59, 130, 246, 0.1); }
.match-btn.matched { border-color: var(--success); background: rgba(76, 175, 80, 0.05); color: var(--success); opacity: 0.5; cursor: default; }
.match-btn.wrong { border-color: var(--error); background: rgba(244, 67, 54, 0.1); animation: shake 0.3s; }

@keyframes shake {
    0%, 100% {transform: translateX(0);}
    25% {transform: translateX(-4px);}
    75% {transform: translateX(4px);}
}

/* ======= Speaking Mode Styles ======= */
.mic-btn {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    border: 1px solid var(--border);
    background: var(--card-bg);
    color: var(--text-sub);
    font-size: 0.9rem;
    cursor: pointer;
    margin: 30px auto;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s;
}

.mic-btn:hover {
    border-color: var(--text-main);
    color: var(--text-main);
}

.mic-btn.listening {
    border-color: var(--error);
    color: var(--error);
    box-shadow: 0 0 15px rgba(244, 67, 54, 0.2);
    animation: pulse 1.5s infinite;
}

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); }
    100% { transform: scale(1); }
}

.speaking-status {
    color: var(--text-sub);
    margin-top: 12px;
    height: 20px;
    font-size: 0.9rem;
    letter-spacing: 0.5px;
}

.score-circle {
    font-size: 2.8rem;
    font-weight: 600;
    color: var(--success);
    margin-bottom: 12px;
}

/* ======= Puzzle Mode Styles ======= */
.puzzle-container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 8px;
    margin-top: 20px;
    min-height: 50px;
}

.letter-tile {
    width: 36px;
    height: 36px;
    display: flex;
    justify-content: center;
    align-items: center;
    border: 1px solid var(--border);
    border-radius: 6px;
    font-weight: 500;
    font-size: 1.1rem;
    cursor: pointer;
    background: var(--card-bg);
    color: var(--text-main);
    user-select: none;
}

.letter-tile:hover { border-color: var(--text-sub); }
.letter-tile.empty { border: 1px dashed #333; color: transparent; cursor: default; }

/* ======= Memory Mode Styles ======= */
.memory-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
    margin-top: 20px;
}

.memory-card {
    background-color: transparent;
    height: 80px;
    perspective: 1000px;
    cursor: pointer;
}

.memory-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform 0.5s;
    transform-style: preserve-3d;
    border-radius: 8px;
}

.memory-card.flipped .memory-inner { transform: rotateY(180deg); }
.memory-card.matched .memory-inner { transform: rotateY(180deg); opacity: 0.4; }

.memory-front, .memory-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    padding: 6px;
    font-size: 0.85rem;
    border: 1px solid var(--border);
}

.memory-back {
    background-color: #1a1a1a;
    color: #444;
    font-size: 1.2rem;
}

.memory-front {
    background-color: var(--card-bg);
    color: var(--accent);
    transform: rotateY(180deg);
    word-break: break-all;
    line-height: 1.3;
}

/* ======= YouGlish Mode Styles ======= */
.yg-open-btn {
    display: block;
    width: 100%;
    padding: 18px;
    margin-bottom: 15px;
    background: #111;
    border: 1px solid #444;
    border-radius: 12px;
    color: white;
    font-size: 0.95rem;
    cursor: pointer;
    text-align: center;
    transition: all 0.2s;
    text-decoration: none;
    letter-spacing: 0.5px;
}

.yg-open-btn:hover { background: #1c1c1c; border-color: var(--text-sub); }
.yg-open-btn .yg-btn-label { font-size: 0.8rem; color: var(--text-sub); margin-top: 6px; }
.yg-tip { color: var(--text-sub); font-size: 0.85rem; margin-bottom: 24px; line-height: 1.6; letter-spacing: 0.5px; }
.yg-word-display { font-size: 2.2rem; color: var(--accent); margin-bottom: 6px; }
.yg-zh-display { font-size: 1.1rem; color: var(--text-sub); margin-bottom: 25px; }

/* ======= Export Menu Styles ======= */
.export-menu {
    position: absolute;
    right: 0;
    top: 100%;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 10px;
    z-index: 100;
    flex-direction: column;
    gap: 8px;
    min-width: 130px;
    box-shadow: 0 4px 16px rgba(0,0,0,0.6);
    display: none;
}

.export-menu.active { display: flex; }

.group-title { font-size: 0.9rem; font-weight: 500; text-transform: uppercase; color: var(--text-sub); letter-spacing: 1px; margin: 25px 0 10px 0; padding-bottom: 6px; border-bottom: 1px solid #222; text-align: left; }
.hidden { display: none !important; }
.flex-row { display: flex; gap: 10px; }
.checkbox-wrapper { display: flex; align-items: center; gap: 10px; cursor: pointer; user-select: none; }
input[type="checkbox"] { accent-color: #ffffff; transform: scale(1.1); }
.mode-badge { font-size: 0.7rem; background: #222; padding: 3px 8px; border-radius: 4px; color: var(--text-sub); letter-spacing: 0.5px; }
.mode-badge.active { background: var(--warning); color: #000; font-weight: bold; }
.import-section { margin-top: 15px; border: 1px dashed var(--border); padding: 15px; border-radius: 8px; }
.import-trigger { font-size: 0.8rem; color: var(--text-sub); text-decoration: underline; cursor: pointer; text-align: right; display: block; margin-bottom: 6px; letter-spacing: 0.5px; }

@keyframes fadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }

.mastery-btn-comp { background-color: #4a148c; color: white; transition: background 0.2s; border: none; }
.mastery-btn-comp:hover { background-color: #6a1b9a; }
.mastery-btn-conn { background-color: #004d40; color: white; transition: background 0.2s; border: none; }
.mastery-btn-conn:hover { background-color: #00695c; }

/* ======= Custom Modal Styles (全新彈窗引擎) ======= */
#silen-modal-overlay {
    position: fixed; top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0, 0, 0, 0.75); backdrop-filter: blur(5px); -webkit-backdrop-filter: blur(5px);
    display: flex; justify-content: center; align-items: center;
    z-index: 9999; opacity: 0; transition: opacity 0.2s ease;
    pointer-events: none;
}
#silen-modal-overlay.show { opacity: 1; pointer-events: auto; }
.silen-modal-box {
    background: var(--card-bg); border: 1px solid var(--border);
    border-radius: 12px; padding: 25px; width: 90%; max-width: 380px;
    box-shadow: 0 10px 40px rgba(0,0,0,0.8);
    transform: translateY(20px) scale(0.95); transition: all 0.2s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}
#silen-modal-overlay.show .silen-modal-box { transform: translateY(0) scale(1); }
.silen-modal-msg { font-size: 1.05rem; color: var(--text-main); margin-bottom: 20px; line-height: 1.6; white-space: pre-wrap; letter-spacing: 0.5px; font-weight: 400;}
.silen-modal-actions { display: flex; justify-content: flex-end; gap: 12px; margin-top: 10px; }
#silen-modal-input, #silen-modal-textarea {
    width: 100%; background: #0a0a0a; border: 1px solid var(--border);
    color: var(--text-main); padding: 12px; border-radius: 8px; margin-bottom: 20px;
    font-family: var(--font-family); font-size: 0.95rem; letter-spacing: 0.5px;
}
#silen-modal-textarea { resize: vertical; min-height: 100px; }

/* ======= 🟢 即時綠點呼吸燈與設定面板 ======= */
.breathing-dot {
    width: 6px; 
    height: 6px; 
    background-color: var(--success); 
    border-radius: 50%;
    box-shadow: 0 0 6px var(--success);
    animation: breath 2s infinite ease-in-out;
}

@keyframes breath {
    0%, 100% { opacity: 0.3; transform: scale(0.8); }
    50% { opacity: 1; transform: scale(1.3); }
}

#silen-settings-overlay {
    position: fixed; top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0, 0, 0, 0.75); backdrop-filter: blur(5px); -webkit-backdrop-filter: blur(5px);
    display: flex; justify-content: center; align-items: center;
    z-index: 9999; opacity: 0; transition: opacity 0.2s ease; pointer-events: none;
}
#silen-settings-overlay.show { opacity: 1; pointer-events: auto; }
#silen-settings-overlay.show .silen-modal-box { transform: translateY(0) scale(1); }

/* 隱藏原生的醜醜 checkbox */
.checkbox-wrapper input[type="checkbox"] {
    appearance: none;
    -webkit-appearance: none;
    width: 22px;
    height: 22px;
    border: 2px solid var(--border);
    border-radius: 4px;
    cursor: pointer;
    position: relative;
    transition: all 0.2s ease;
    flex-shrink: 0; 
}


.checkbox-wrapper input[type="checkbox"]:checked {
    background-color: var(--accent);
    border-color: var(--accent);
}


.checkbox-wrapper input[type="checkbox"]:checked::after {
    content: '✔';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: #000; /* 勾勾顏色 */
    font-size: 14px;
    font-weight: bold;
}


.checkbox-wrapper:hover input[type="checkbox"] {
    border-color: var(--accent);
}

/* ========================================================= */
/* 💎 頂級 UX 升級：Liquid Glass、微動效與畫面呼吸感 */
/* ========================================================= */

/* 1. Liquid Glass (毛玻璃) 卡片質感 */
.card, .store-card, .acc-card, .silen-modal-box {
    background: rgba(20, 20, 20, 0.45) !important; /* 半透明深色底 */
    backdrop-filter: blur(16px) saturate(120%); /* 核心：玻璃模糊與色彩增艷 */
    -webkit-backdrop-filter: blur(16px) saturate(120%); /* 支援 Safari */
    border: 1px solid rgba(255, 255, 255, 0.08) !important; /* 極微弱的玻璃邊緣反光 */
    box-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.4) !important; /* 深邃陰影襯托立體感 */
    transition: transform 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
}

/* 2. 卡片懸浮光暈 (Hover Glow) */
.store-card:hover, .acc-card:hover, .book-item:hover {
    transform: translateY(-3px);
    box-shadow: 0 12px 40px 0 rgba(0, 0, 0, 0.6), 0 0 15px rgba(255, 255, 255, 0.05) !important;
    border-color: rgba(255, 255, 255, 0.2) !important;
}

/* 3. 按鈕的 3D 觸覺回饋 (Micro-interactions) */
.btn {
    transition: all 0.2s cubic-bezier(0.25, 0.8, 0.25, 1) !important;
    position: relative;
    overflow: hidden;
}
.btn:hover {
    box-shadow: 0 0 15px rgba(255, 255, 255, 0.15) !important; /* 按鈕微泛光 */
}
.btn:active {
    transform: scale(0.96) translateY(2px) !important; /* 點擊時瞬間微縮+下沉 */
    box-shadow: 0 2px 5px rgba(0,0,0,0.2) !important; /* 陰影縮小，模擬壓下實體鍵 */
    opacity: 0.8;
}

/* 4. 畫面切換的「呼吸感」(Fade In & Slide Up) */
/* 只要畫面移除 hidden 類別，就會自動觸發這個優雅的浮現動畫 */
div[id^="view-"]:not(.hidden) {
    animation: viewFadeIn 0.35s cubic-bezier(0.2, 0.8, 0.2, 1) forwards;
}

@keyframes viewFadeIn {
    from {
        opacity: 0;
        transform: translateY(15px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* 5. 側邊導覽列 (Sidebar) 極簡白化與收納匣樣式 */
.sidebar {
    background: rgba(15, 15, 15, 0.85) !important;
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
}
.sidebar-item {
    border-left: 3px solid transparent !important; /* 移除所有預設顏色 */
    color: var(--text-sub) !important; /* 預設偏灰 */
}
.sidebar-item:hover {
    background: rgba(255, 255, 255, 0.05) !important;
    border-left: 3px solid #fff !important; /* 統一變成白色指示線 */
    color: #fff !important;
}
.sidebar-submenu {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.35s cubic-bezier(0.2, 0.8, 0.2, 1);
    background: rgba(0, 0, 0, 0.3); /* 子選單底色更深一點點 */
}
.sidebar-submenu.expanded {
    max-height: 250px; /* 展開高度 */
}
.sidebar-submenu .sidebar-item {
    padding-left: 45px; /* 子選項向右縮進 */
    font-size: 0.95rem;
}
.sidebar-submenu-toggle {
    display: flex;
    justify-content: space-between;
    align-items: center;
}
.sidebar-submenu-toggle .arrow {
    transition: transform 0.3s ease;
    font-size: 0.8rem;
}
.sidebar-submenu-toggle.expanded .arrow {
    transform: rotate(180deg);
}