* {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
    }

    body {
        font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
        min-height: 100vh;
        color: #333;
    }

    .container {
        max-width: 1200px;
        margin: 0 auto;
        padding: 20px;
        min-height: 100vh;
        display: flex;
        flex-direction: column;
    }

    .header {
        text-align: center;
        margin-bottom: 30px;
        color: white;
    }

    .header h1 {
        font-size: 2.5rem;
        margin-bottom: 10px;
        text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
    }

    .stats-bar {
        background: rgba(255,255,255,0.9);
        padding: 15px;
        border-radius: 10px;
        display: flex;
        justify-content: space-between;
        align-items: center;
        margin-bottom: 20px;
        box-shadow: 0 4px 15px rgba(0,0,0,0.1);
        flex-wrap: wrap;
        gap: 10px;
    }

    .mode-selector {
        display: flex;
        gap: 15px;
        margin-bottom: 20px;
        justify-content: center;
    }

    .mode-btn {
        padding: 12px 30px;
        border: none;
        border-radius: 25px;
        cursor: pointer;
        font-size: 16px;
        font-weight: 600;
        transition: all 0.3s ease;
        background: rgba(255,255,255,0.2);
        color: white;
        border: 2px solid rgba(255,255,255,0.3);
    }

    .mode-btn.active {
        background: white;
        color: #667eea;
        transform: translateY(-2px);
        box-shadow: 0 4px 15px rgba(0,0,0,0.2);
    }

    .mode-btn:hover:not(.active) {
        background: rgba(255,255,255,0.3);
        transform: translateY(-1px);
    }

    .main-content {
        flex: 1;
        display: flex;
        justify-content: center;
        align-items: center;
    }

    .card-container {
        background: white;
        border-radius: 20px;
        box-shadow: 0 10px 30px rgba(0,0,0,0.2);
        padding: 40px;
        min-height: 400px;
        width: 100%;
        max-width: 600px;
        display: flex;
        flex-direction: column;
        justify-content: center;
        position: relative;
        overflow: hidden;
    }

    .flashcard {
        perspective: 1000px;
        height: 300px;
        cursor: pointer;
    }

    .card-inner {
        position: relative;
        width: 100%;
        height: 100%;
        text-align: center;
        transition: transform 0.6s;
        transform-style: preserve-3d;
    }

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

    .card-front, .card-back {
        position: absolute;
        width: 100%;
        height: 100%;
        backface-visibility: hidden;
        display: flex;
        align-items: center;
        justify-content: center;
        border-radius: 15px;
        padding: 20px;
    }

    .card-front {
        background: linear-gradient(135deg, #ff9a56 0%, #ff6b95 100%);
        color: white;
    }

    .card-back {
        background: linear-gradient(135deg, #a8edea 0%, #fed6e3 100%);
        color: #333;
        transform: rotateY(180deg);
    }

    .learning-mode {
        text-align: center;
    }

    .question-text {
        font-size: 1.8rem;
        margin-bottom: 20px;
        font-weight: 600;
    }

    .answer-text {
        font-size: 1.5rem;
        font-weight: 500;
    }

    .navigation {
        display: flex;
        justify-content: space-between;
        align-items: center;
        margin-top: 30px;
        padding: 0 20px;
    }

    .nav-btn {
        padding: 12px 24px;
        border: none;
        border-radius: 25px;
        cursor: pointer;
        font-size: 16px;
        font-weight: 600;
        transition: all 0.3s ease;
        background: #667eea;
        color: white;
    }

    .nav-btn:hover:not(:disabled) {
        background: #5a67d8;
        transform: translateY(-2px);
        box-shadow: 0 4px 15px rgba(0,0,0,0.2);
    }

    .nav-btn:disabled {
        opacity: 0.5;
        cursor: not-allowed;
    }

    .progress-indicator {
        font-size: 18px;
        font-weight: 600;
        color: #667eea;
    }

    .settings-btn {
        position: fixed;
        top: 20px;
        right: 20px;
        background: rgba(255,255,255,0.2);
        border: 2px solid rgba(255,255,255,0.3);
        color: white;
        border-radius: 50%;
        width: 60px;
        height: 60px;
        cursor: pointer;
        font-size: 24px;
        transition: all 0.3s ease;
        display: flex;
        align-items: center;
        justify-content: center;
    }

    .settings-btn:hover {
        background: rgba(255,255,255,0.3);
        transform: rotate(45deg);
    }

    .settings-drawer {
        position: fixed;
        top: 0;
        right: -400px;
        width: 350px;
        height: 100vh;
        background: white;
        box-shadow: -5px 0 20px rgba(0,0,0,0.3);
        transition: right 0.3s ease;
        padding: 20px;
        overflow-y: auto;
        z-index: 1000;
    }

    .settings-drawer.open {
        right: 0;
    }

    .settings-header {
        display: flex;
        justify-content: space-between;
        align-items: center;
        margin-bottom: 30px;
        padding-bottom: 15px;
        border-bottom: 2px solid #eee;
    }

    .close-btn {
        background: none;
        border: none;
        font-size: 24px;
        cursor: pointer;
        color: #666;
    }

    .setting-item {
        margin-bottom: 25px;
    }

    .setting-label {
        display: block;
        margin-bottom: 8px;
        font-weight: 600;
        color: #333;
    }

    .setting-input {
        width: 100%;
        padding: 10px;
        border: 2px solid #ddd;
        border-radius: 8px;
        font-size: 16px;
    }

    .setting-input:focus {
        outline: none;
        border-color: #667eea;
    }

    .auto-play-controls {
        background: #f8f9fa;
        padding: 20px;
        border-radius: 10px;
        margin-bottom: 20px;
    }

    .play-pause-btn {
        background: #28a745;
        color: white;
        border: none;
        padding: 10px 20px;
        border-radius: 8px;
        cursor: pointer;
        font-size: 16px;
        margin-right: 10px;
        transition: all 0.3s ease;
    }

    .play-pause-btn:hover {
        background: #218838;
    }

    .play-pause-btn.paused {
        background: #ffc107;
        color: #333;
    }

    .reset-btn {
        background: #dc3545;
        color: white;
        border: none;
        padding: 10px 20px;
        border-radius: 8px;
        cursor: pointer;
        font-size: 16px;
        transition: all 0.3s ease;
    }

    .reset-btn:hover {
        background: #c82333;
    }

    .score-display {
        font-size: 18px;
        font-weight: 600;
        color: #28a745;
    }

    .question-counter {
        font-size: 16px;
        color: #666;
    }

    .flip-hint {
        position: absolute;
        bottom: 10px;
        right: 10px;
        background: rgba(0,0,0,0.7);
        color: white;
        padding: 5px 10px;
        border-radius: 15px;
        font-size: 12px;
        opacity: 0.8;
    }

    @keyframes bounce {
        0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
        40% { transform: translateY(-10px); }
        60% { transform: translateY(-5px); }
    }

    .bounce {
        animation: bounce 1s ease-in-out;
    }

    @media (max-width: 768px) {
        .container {
            padding: 10px;
        }

        .header h1 {
            font-size: 2rem;
        }

        .card-container {
            padding: 20px;
            min-height: 300px;
        }

        .question-text {
            font-size: 1.4rem;
        }

        .answer-text {
            font-size: 1.2rem;
        }

        .settings-drawer {
            width: 90vw;
            right: -90vw;
        }

        .stats-bar {
            flex-direction: column;
            gap: 10px;
            text-align: center;
        }

        .mode-selector {
            flex-direction: column;
            align-items: center;
        }
    }