:root {
    --bg: #fafafa;
    --surface: #ffffff;
    --border: #e5e5e5;
    --text: #1a1a1a;
    --text-secondary: #666;
    --accent: #2563eb;
    --accent-light: #eff6ff;
    --success: #22c55e;
    --success-light: #dcfce7;
    --error: #ef4444;
    --error-light: #fef2f2;
    --haydn: #fecaca;
    --mozart: #fef08a;
    --beethoven: #bbf7d0;
}

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

body {
    font-family: 'Inter', -apple-system, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 24px;
}

/* Header */
header {
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 16px 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-family: 'Source Serif 4', Georgia, serif;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text);
    text-decoration: none;
}

.back-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    gap: 6px;
}

.back-link:hover {
    color: var(--accent);
}

/* Page Header */
.page-header {
    padding: 32px 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
}

.page-header h1 {
    font-family: 'Source Serif 4', Georgia, serif;
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 8px;
}

.page-header p {
    color: var(--text-secondary);
}

/* Main */
main {
    padding: 32px 0;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 20px;
    border-radius: 6px;
    font-size: 0.9375rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    border: none;
    text-decoration: none;
}

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

.btn-primary:hover {
    background: #1d4ed8;
}

.btn-secondary {
    background: var(--surface);
    color: var(--text);
    border: 1px solid var(--border);
}

.btn-secondary:hover {
    background: var(--bg);
}

.btn-success {
    background: var(--success);
    color: white;
}

.btn-small {
    padding: 6px 12px;
    font-size: 0.8125rem;
}

/* Cards */
.card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 24px;
}

/* Progress */
.progress-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    padding: 16px 20px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
}

.progress-info {
    display: flex;
    align-items: center;
    gap: 16px;
}

.progress-bar-container {
    width: 200px;
    height: 8px;
    background: var(--bg);
    border-radius: 4px;
    overflow: hidden;
}

.progress-bar-fill {
    height: 100%;
    background: var(--accent);
    border-radius: 4px;
    transition: width 0.3s;
}

.progress-text {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Result */
.result-box {
    padding: 24px;
    border-radius: 8px;
    text-align: center;
    margin-top: 24px;
}

.result-box.success {
    background: var(--success-light);
    border: 1px solid var(--success);
}

.result-box.error {
    background: var(--error-light);
    border: 1px solid var(--error);
}

.result-score {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 8px;
}

.result-box.success .result-score {
    color: var(--success);
}

.result-box.error .result-score {
    color: var(--error);
}

/* Input */
input[type="text"] {
    padding: 8px 12px;
    border: 1px solid var(--border);
    border-radius: 4px;
    font-size: 0.9375rem;
    font-family: inherit;
    transition: border-color 0.2s;
}

input[type="text"]:focus {
    outline: none;
    border-color: var(--accent);
}

input[type="text"].correct {
    border-color: var(--success);
    background: var(--success-light);
}

input[type="text"].incorrect {
    border-color: var(--error);
    background: var(--error-light);
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.fade-in {
    animation: fadeIn 0.3s ease;
}

/* Responsive */
@media (max-width: 768px) {
    .container {
        padding: 0 16px;
    }

    .page-header {
        padding: 24px 0;
    }

    .page-header h1 {
        font-size: 1.5rem;
    }

    main {
        padding: 24px 0;
    }

    .btn {
        padding: 12px 16px;
        font-size: 0.875rem;
    }
}

@media (max-width: 600px) {
    .progress-header {
        flex-direction: column;
        gap: 16px;
        padding: 12px 16px;
    }

    .progress-info {
        flex-direction: column;
        width: 100%;
        gap: 8px;
    }

    .progress-bar-container {
        width: 100%;
    }

    .result-box {
        padding: 20px 16px;
    }

    .result-score {
        font-size: 1.75rem;
    }
}