* {
    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;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 500px;
}

h1 {
    text-align: center;
    color: white;
    margin-bottom: 20px;
    font-size: 2.2em;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

.progress-bar {
    background: rgba(255, 255, 255, 0.2);
    border-radius: 10px;
    padding: 10px 20px;
    margin-bottom: 20px;
    text-align: center;
}

#progress-text {
    color: white;
    font-size: 0.9em;
    font-weight: 500;
}

.card {
    background: white;
    border-radius: 15px;
    padding: 40px 30px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
    text-align: center;
}

.word-display {
    margin-bottom: 30px;
    min-height: 120px;
    display: flex;
    flex-direction: column;
    justify-content: center;
}

.word {
    font-size: 2.5em;
    font-weight: bold;
    color: #333;
    margin-bottom: 15px;
    word-wrap: break-word;
}

.translation {
    font-size: 1.8em;
    color: #666;
    font-style: italic;
    opacity: 1;
    transition: opacity 0.3s ease;
}

.translation.hidden {
    opacity: 0;
    height: 0;
    margin: 0;
}

.input-section {
    margin-bottom: 25px;
}

.answer-input {
    width: 100%;
    padding: 12px 15px;
    font-size: 1.1em;
    border: 2px solid #dee2e6;
    border-radius: 8px;
    outline: none;
    transition: border-color 0.3s ease;
}

.answer-input:focus {
    border-color: #667eea;
}

.feedback {
    font-size: 1.2em;
    font-weight: 600;
    margin-top: 10px;
    padding: 10px;
    border-radius: 8px;
    opacity: 1;
    transition: opacity 0.3s ease;
}

.feedback.hidden {
    opacity: 0;
    height: 0;
    margin: 0;
    padding: 0;
}

.feedback.correct {
    background-color: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.feedback.incorrect {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.feedback.error {
    background-color: #fff3cd;
    color: #856404;
    border: 1px solid #ffeaa7;
}

.controls {
    display: flex;
    gap: 15px;
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    padding: 12px 30px;
    border: none;
    border-radius: 25px;
    font-size: 1.1em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    min-width: 140px;
}

.btn-primary {
    background: #667eea;
    color: white;
}

.btn-primary:hover {
    background: #5a6fd8;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-secondary {
    background: #f8f9fa;
    color: #333;
    border: 2px solid #dee2e6;
}

.btn-secondary:hover {
    background: #e9ecef;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.btn-neutral {
    background: #6c757d;
    color: white;
}

.btn-neutral:hover {
    background: #5a6268;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(108, 117, 125, 0.4);
}

.btn.hidden {
    display: none;
}

.btn:active {
    transform: translateY(0);
}

@media (max-width: 480px) {
    .container {
        padding: 10px;
    }

    h1 {
        font-size: 1.8em;
        margin-bottom: 20px;
    }

    .card {
        padding: 30px 20px;
    }

    .word {
        font-size: 2em;
    }

    .translation {
        font-size: 1.4em;
    }

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

    .btn {
        width: 100%;
        max-width: 200px;
    }
}