/* CSS Variables for theming */
:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --primary-light: #e0e7ff;
    --secondary-color: #64748b;
    --success-color: #22c55e;
    --success-light: #dcfce7;
    --error-color: #ef4444;
    --error-light: #fee2e2;
    --warning-color: #f59e0b;
    --background: #f8fafc;
    --surface: #ffffff;
    --surface-hover: #f1f5f9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --transition: all 0.2s ease;
}

/* Reset and base styles */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* App Container */
.app-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
header {
    text-align: center;
    padding: 30px 20px;
    background: linear-gradient(135deg, var(--primary-color), #8b5cf6);
    border-radius: var(--radius-lg);
    color: white;
    margin-bottom: 24px;
    box-shadow: var(--shadow-lg);
}

header h1 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 8px;
}

header .subtitle {
    opacity: 0.9;
    font-size: 1.1rem;
}

/* Main content */
main {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 24px;
}

/* Section styling */
section {
    background: var(--surface);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-md);
}

section h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}

section h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 12px;
    color: var(--text-primary);
}

/* Settings Panel */
.settings-panel {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 16px;
}

.setting-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.setting-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
}

select {
    padding: 10px 14px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background: var(--surface);
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' fill='%2364748b' viewBox='0 0 16 16'%3E%3Cpath d='M8 11L3 6h10l-5 5z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 36px;
}

select:hover {
    border-color: var(--primary-color);
}

select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px var(--primary-light);
}

/* Mode Selection */
.mode-selection {
    text-align: center;
}

.mode-buttons {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
    margin-top: 16px;
}

.mode-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    padding: 20px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--surface);
    cursor: pointer;
    transition: var(--transition);
}

.mode-btn:hover {
    border-color: var(--primary-color);
    background: var(--surface-hover);
}

.mode-btn.active {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.mode-icon {
    font-size: 2rem;
}

.mode-name {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
}

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

/* Game Panel */
.game-panel {
    transition: var(--transition);
}

.game-panel.hidden {
    display: none;
}

/* Scale selector */
.scale-selector {
    margin-bottom: 20px;
}

.scale-selector label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 6px;
}

.scale-selector select {
    width: 100%;
}

/* Scale Info */
.scale-info {
    background: var(--surface-hover);
    border-radius: var(--radius-md);
    padding: 16px;
    margin-bottom: 20px;
}

.scale-info h3 {
    color: var(--primary-color);
    margin-bottom: 8px;
}

.scale-info p {
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.scale-intervals,
.scale-notes {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-top: 8px;
}

.scale-intervals .label,
.scale-notes .label {
    font-weight: 500;
    color: var(--text-secondary);
    min-width: 70px;
}

#scale-intervals-display,
#scale-notes-display {
    font-family: 'Courier New', monospace;
    font-weight: 600;
    color: var(--text-primary);
    background: var(--surface);
    padding: 4px 10px;
    border-radius: var(--radius-sm);
}

/* Play Controls */
.play-controls {
    display: flex;
    gap: 12px;
    margin-bottom: 24px;
    flex-wrap: wrap;
}

/* Buttons */
.primary-btn,
.secondary-btn,
.danger-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

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

.primary-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

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

.primary-btn.large {
    padding: 16px 32px;
    font-size: 1.125rem;
}

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

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

.danger-btn {
    background: var(--error-light);
    color: var(--error-color);
    border: 2px solid transparent;
}

.danger-btn:hover {
    background: var(--error-color);
    color: white;
}

.btn-icon {
    font-size: 0.875em;
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none !important;
}

/* Piano */
.piano-container {
    margin-top: 20px;
}

.piano {
    display: flex;
    justify-content: center;
    position: relative;
    height: 140px;
    margin: 0 auto;
    max-width: 100%;
    overflow-x: auto;
    padding: 10px 0;
}

.key {
    position: relative;
    cursor: pointer;
    transition: var(--transition);
}

.key.white {
    width: 40px;
    height: 130px;
    background: white;
    border: 1px solid #ccc;
    border-radius: 0 0 var(--radius-sm) var(--radius-sm);
    z-index: 1;
    margin: 0 1px;
}

.key.white:hover {
    background: #f0f0f0;
}

.key.white.active {
    background: var(--primary-light);
    border-color: var(--primary-color);
}

.key.white.playing {
    background: var(--success-light);
    border-color: var(--success-color);
    transform: translateY(2px);
}

.key.black {
    width: 28px;
    height: 85px;
    background: #333;
    border-radius: 0 0 var(--radius-sm) var(--radius-sm);
    position: absolute;
    z-index: 2;
}

.key.black:hover {
    background: #444;
}

.key.black.active {
    background: var(--primary-color);
}

.key.black.playing {
    background: var(--success-color);
    transform: translateY(2px);
}

.key .note-label {
    position: absolute;
    bottom: 8px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--text-secondary);
    pointer-events: none;
}

.key.black .note-label {
    color: white;
}

/* Quiz Panel */
.quiz-status {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 12px;
    margin-bottom: 24px;
}

.status-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 12px;
    background: var(--surface-hover);
    border-radius: var(--radius-md);
}

.status-label {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.status-value {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

.quiz-area {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
}

.quiz-prompt {
    text-align: center;
    padding: 20px;
    background: var(--surface-hover);
    border-radius: var(--radius-md);
    width: 100%;
}

.quiz-prompt p {
    font-size: 1.1rem;
    color: var(--text-primary);
}

.answer-options {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
    width: 100%;
}

.answer-btn {
    padding: 16px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--surface);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.answer-btn:hover:not(:disabled) {
    border-color: var(--primary-color);
    background: var(--primary-light);
}

.answer-btn.correct {
    border-color: var(--success-color);
    background: var(--success-light);
    color: var(--success-color);
}

.answer-btn.incorrect {
    border-color: var(--error-color);
    background: var(--error-light);
    color: var(--error-color);
}

.quiz-feedback {
    padding: 16px;
    border-radius: var(--radius-md);
    text-align: center;
    width: 100%;
}

.quiz-feedback.hidden {
    display: none;
}

.quiz-feedback.correct {
    background: var(--success-light);
    color: var(--success-color);
}

.quiz-feedback.incorrect {
    background: var(--error-light);
    color: var(--error-color);
}

.quiz-controls {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-top: 20px;
}

/* Progress Section */
.progress-section {
    text-align: center;
}

.progress-stats {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
    margin-bottom: 24px;
}

.stat-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    padding: 16px;
    background: var(--surface-hover);
    border-radius: var(--radius-md);
}

.stat-icon {
    font-size: 1.5rem;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.stat-label {
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.scale-mastery {
    margin-bottom: 20px;
}

.mastery-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
    gap: 12px;
    margin-top: 16px;
}

.mastery-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 6px;
    padding: 12px;
    background: var(--surface-hover);
    border-radius: var(--radius-md);
}

.mastery-item .scale-name {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-primary);
}

.mastery-bar {
    width: 100%;
    height: 6px;
    background: var(--border-color);
    border-radius: 3px;
    overflow: hidden;
}

.mastery-fill {
    height: 100%;
    background: var(--primary-color);
    border-radius: 3px;
    transition: width 0.3s ease;
}

.mastery-fill.high {
    background: var(--success-color);
}

.mastery-fill.medium {
    background: var(--warning-color);
}

.mastery-fill.low {
    background: var(--error-color);
}

.mastery-percent {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-secondary);
}

/* Footer */
footer {
    text-align: center;
    padding: 24px;
    margin-top: 24px;
    border-top: 1px solid var(--border-color);
}

footer a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.875rem;
    transition: var(--transition);
}

footer a:hover {
    color: var(--primary-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .app-container {
        padding: 12px;
    }

    header {
        padding: 24px 16px;
    }

    header h1 {
        font-size: 1.5rem;
    }

    section {
        padding: 16px;
    }

    .settings-panel {
        grid-template-columns: 1fr;
    }

    .mode-buttons {
        grid-template-columns: 1fr;
    }

    .play-controls {
        flex-direction: column;
    }

    .primary-btn,
    .secondary-btn {
        width: 100%;
    }

    .piano {
        height: 120px;
    }

    .key.white {
        width: 32px;
        height: 110px;
    }

    .key.black {
        width: 22px;
        height: 70px;
    }

    .quiz-status {
        grid-template-columns: repeat(3, 1fr);
        gap: 8px;
    }

    .status-item {
        padding: 8px;
    }

    .status-value {
        font-size: 1rem;
    }

    .answer-options {
        grid-template-columns: 1fr;
    }

    .progress-stats {
        grid-template-columns: repeat(2, 1fr);
        gap: 12px;
    }

    .stat-card {
        padding: 12px;
    }

    .stat-value {
        font-size: 1.25rem;
    }

    .mastery-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.25rem;
    }

    .subtitle {
        font-size: 0.9rem;
    }

    .key.white {
        width: 26px;
        height: 100px;
    }

    .key.black {
        width: 18px;
        height: 60px;
    }

    .key .note-label {
        font-size: 0.6rem;
    }

    .progress-stats {
        grid-template-columns: 1fr 1fr;
    }
}

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

.playing-animation {
    animation: pulse 0.3s ease;
}

/* Accessibility */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Focus styles */
button:focus-visible,
select:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}