/* ===== GEPT 練習平台 - 樣式系統 ===== */

/* 變數定義 */
:root {
    --bg-gradient: linear-gradient(135deg, #1a1a2e 0%, #16213e 50%, #0f3460 100%);
    --card-bg: rgba(255, 255, 255, 0.08);
    --card-border: rgba(255, 255, 255, 0.15);
    --card-hover: rgba(255, 255, 255, 0.12);
    --primary: #4facfe;
    --secondary: #00f2fe;
    --accent-orange: #f97316;
    --accent-purple: #a855f7;
    --accent-green: #22c55e;
    --accent-pink: #ec4899;
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.7);
    --text-muted: rgba(255, 255, 255, 0.5);
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-hover: 0 16px 48px rgba(0, 0, 0, 0.4);
    --radius: 20px;
    --radius-sm: 12px;
}

/* 重置與基礎 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Noto Sans TC', 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-gradient);
    min-height: 100vh;
    color: var(--text-primary);
    line-height: 1.6;
}

/* 容器 */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

/* 頂部導航 */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 40px;
    background: var(--card-bg);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--card-border);
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    transition: all 0.3s ease;
}

.nav-link:hover {
    color: var(--text-primary);
    background: var(--card-bg);
}

/* Hero 區塊 */
.hero {
    text-align: center;
    padding: 80px 20px 60px;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: 20px;
    background: linear-gradient(90deg, var(--primary), var(--secondary), var(--accent-purple));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero .subtitle {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.hero .description {
    font-size: 1rem;
    color: var(--text-muted);
}

/* 功能卡片網格 */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 30px;
    padding: 40px 20px;
    max-width: 1000px;
    margin: 0 auto;
}

/* 功能卡片 */
.card {
    background: var(--card-bg);
    backdrop-filter: blur(15px);
    border: 1px solid var(--card-border);
    border-radius: var(--radius);
    padding: 40px 30px;
    text-align: center;
    text-decoration: none;
    color: var(--text-primary);
    transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    position: relative;
    overflow: hidden;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    opacity: 0;
    transition: opacity 0.3s ease;
}

.card:hover {
    transform: translateY(-10px) scale(1.02);
    background: var(--card-hover);
    box-shadow: var(--shadow-hover);
}

.card:hover::before {
    opacity: 1;
}

.card-icon {
    font-size: 3.5rem;
    margin-bottom: 20px;
    display: block;
}

.card h2 {
    font-size: 1.5rem;
    margin-bottom: 8px;
    font-weight: 600;
}

.card .level-tag {
    display: inline-block;
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.85rem;
    margin-bottom: 15px;
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-secondary);
}

.card p {
    color: var(--text-muted);
    font-size: 0.95rem;
}

/* 卡片顏色變體 */
.card.elementary { --card-accent: var(--accent-green); }
.card.intermediate { --card-accent: var(--accent-orange); }
.card.vocabulary { --card-accent: var(--accent-purple); }
.card.history { --card-accent: var(--accent-pink); }

.card.elementary::before { background: var(--accent-green); }
.card.intermediate::before { background: var(--accent-orange); }
.card.vocabulary::before { background: linear-gradient(90deg, var(--accent-purple), var(--accent-pink)); }
.card.history::before { background: var(--accent-pink); }

/* 頁腳 */
.footer {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-muted);
    font-size: 0.9rem;
    border-top: 1px solid var(--card-border);
    margin-top: 40px;
}

/* ===== 練習頁面樣式 ===== */

.practice-header {
    text-align: center;
    padding: 40px 20px;
}

.practice-header h1 {
    font-size: 2.2rem;
    margin-bottom: 10px;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.practice-header .subtitle {
    color: var(--text-secondary);
}

/* 題目類型選擇 */
.type-selector {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 40px;
    flex-wrap: wrap;
}

.type-btn {
    padding: 12px 30px;
    border: 2px solid var(--card-border);
    background: var(--card-bg);
    color: var(--text-primary);
    border-radius: 30px;
    cursor: pointer;
    font-size: 1rem;
    transition: all 0.3s ease;
    backdrop-filter: blur(10px);
}

.type-btn:hover {
    border-color: var(--primary);
    background: rgba(79, 172, 254, 0.1);
}

.type-btn.active {
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    border-color: transparent;
    font-weight: 600;
}

/* 題目區域 */
.question-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 20px;
}

.question-card {
    background: var(--card-bg);
    backdrop-filter: blur(15px);
    border: 1px solid var(--card-border);
    border-radius: var(--radius);
    padding: 40px;
    margin-bottom: 30px;
}

.question-number {
    display: inline-block;
    padding: 6px 16px;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: 20px;
}

.question-text {
    font-size: 1.3rem;
    margin-bottom: 30px;
    line-height: 1.8;
}

.audio-btn {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 12px 24px;
    background: linear-gradient(90deg, var(--accent-purple), var(--accent-pink));
    border: none;
    border-radius: 30px;
    color: white;
    font-size: 1rem;
    cursor: pointer;
    margin-bottom: 25px;
    transition: transform 0.3s, box-shadow 0.3s;
}

.audio-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 25px rgba(168, 85, 247, 0.4);
}

/* 選項 */
.options {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.option {
    display: flex;
    align-items: center;
    gap: 15px;
    padding: 18px 24px;
    background: rgba(255, 255, 255, 0.05);
    border: 2px solid transparent;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all 0.3s ease;
}

.option:hover {
    background: rgba(79, 172, 254, 0.1);
    border-color: var(--primary);
}

.option.selected {
    background: rgba(79, 172, 254, 0.15);
    border-color: var(--primary);
}

.option.correct {
    background: rgba(34, 197, 94, 0.2);
    border-color: var(--accent-green);
}

.option.wrong {
    background: rgba(239, 68, 68, 0.2);
    border-color: #ef4444;
}

.option-label {
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    font-weight: 600;
}

/* 按鈕樣式 */
.btn {
    padding: 14px 40px;
    border: none;
    border-radius: 30px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-primary {
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(79, 172, 254, 0.4);
}

.btn-secondary {
    background: var(--card-bg);
    border: 2px solid var(--card-border);
    color: var(--text-primary);
}

.btn-secondary:hover {
    border-color: var(--primary);
}

.action-buttons {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-top: 30px;
    flex-wrap: wrap;
}

/* 分數顯示 */
.score-display {
    text-align: center;
    padding: 20px;
    background: var(--card-bg);
    border-radius: var(--radius);
    margin-bottom: 30px;
}

.score-display .score {
    font-size: 3rem;
    font-weight: 800;
    background: linear-gradient(90deg, var(--accent-green), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* ===== 單字閃卡樣式 ===== */

.flashcard-container {
    max-width: 500px;
    margin: 0 auto;
    padding: 40px 20px;
}

.flashcard {
    width: 100%;
    height: 300px;
    perspective: 1000px;
    cursor: pointer;
    margin-bottom: 30px;
}

.flashcard-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.6s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    transform-style: preserve-3d;
}

.flashcard.flipped .flashcard-inner {
    transform: rotateY(180deg);
}

.flashcard-front,
.flashcard-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: var(--radius);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 30px;
    background: var(--card-bg);
    backdrop-filter: blur(15px);
    border: 1px solid var(--card-border);
}

.flashcard-back {
    transform: rotateY(180deg);
    background: linear-gradient(135deg, rgba(79, 172, 254, 0.15), rgba(0, 242, 254, 0.15));
}

.flashcard-word {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 15px;
}

.flashcard-phonetic {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.flashcard-pos {
    display: inline-block;
    padding: 6px 16px;
    background: rgba(168, 85, 247, 0.3);
    border-radius: 20px;
    font-size: 0.9rem;
    color: var(--accent-purple);
}

.flashcard-meaning {
    font-size: 1.8rem;
    text-align: center;
    line-height: 1.6;
}

.flashcard-hint {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: 20px;
}

.speak-btn {
    position: absolute;
    top: 20px;
    right: 20px;
    width: 50px;
    height: 50px;
    border: none;
    border-radius: 50%;
    background: linear-gradient(90deg, var(--accent-purple), var(--accent-pink));
    color: white;
    font-size: 1.3rem;
    cursor: pointer;
    transition: transform 0.3s, box-shadow 0.3s;
}

.speak-btn:hover {
    transform: scale(1.1);
    box-shadow: 0 8px 25px rgba(168, 85, 247, 0.4);
}

/* 單字操作按鈕 */
.flashcard-actions {
    display: flex;
    justify-content: center;
    gap: 20px;
}

.action-btn {
    padding: 16px 40px;
    border: none;
    border-radius: 30px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.action-btn.know {
    background: linear-gradient(90deg, var(--accent-green), #16a34a);
    color: white;
}

.action-btn.dont-know {
    background: linear-gradient(90deg, #ef4444, #dc2626);
    color: white;
}

.action-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.3);
}

/* 進度條 */
.progress-bar {
    width: 100%;
    height: 8px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 10px;
    margin-bottom: 30px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    border-radius: 10px;
    transition: width 0.3s ease;
}

.progress-text {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 20px;
}

/* ===== 學習歷史頁面 ===== */

.history-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 40px 20px;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 40px;
}

.stat-card {
    background: var(--card-bg);
    backdrop-filter: blur(15px);
    border: 1px solid var(--card-border);
    border-radius: var(--radius);
    padding: 30px;
    text-align: center;
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 10px;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 1rem;
}

.history-list {
    background: var(--card-bg);
    backdrop-filter: blur(15px);
    border: 1px solid var(--card-border);
    border-radius: var(--radius);
    overflow: hidden;
}

.history-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 30px;
    border-bottom: 1px solid var(--card-border);
    transition: background 0.3s;
}

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

.history-item:hover {
    background: rgba(255, 255, 255, 0.05);
}

.history-date {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.history-type {
    font-weight: 600;
}

.history-score {
    padding: 6px 16px;
    background: linear-gradient(90deg, var(--accent-green), #16a34a);
    border-radius: 20px;
    font-weight: 600;
}

/* 返回按鈕 */
.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 12px 24px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 30px;
    color: var(--text-primary);
    text-decoration: none;
    transition: all 0.3s ease;
    margin-bottom: 30px;
}

.back-btn:hover {
    background: var(--card-hover);
    border-color: var(--primary);
}

/* ===== 響應式設計 ===== */

@media (max-width: 768px) {
    .hero h1 {
        font-size: 2rem;
    }

    .hero .subtitle {
        font-size: 1rem;
    }

    .card-grid {
        grid-template-columns: 1fr;
        padding: 20px;
    }

    .card {
        padding: 30px 20px;
    }

    .header {
        padding: 15px 20px;
        flex-direction: column;
        gap: 15px;
    }

    .question-card {
        padding: 25px;
    }

    .question-text {
        font-size: 1.1rem;
    }

    .flashcard {
        height: 250px;
    }

    .flashcard-word {
        font-size: 2rem;
    }

    .flashcard-meaning {
        font-size: 1.4rem;
    }

    .flashcard-actions {
        flex-direction: column;
    }

    .action-btn {
        width: 100%;
    }
}

/* 動畫 */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.animate-in {
    animation: fadeInUp 0.6s ease forwards;
}

.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }

/* 隱藏類別 */
.hidden {
    display: none !important;
}