/* ============================================
   Global Styles
   ============================================ */

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

:root {
    --color-primary: #3b82f6;
    --color-secondary: #10b981;
    --color-tertiary: #f59e0b;
    --color-dark: #1f2937;
    --color-light: #f9fafb;
    --color-gray: #6b7280;
    --spacing-unit: 1rem;
    --border-radius: 0.5rem;
    --transition-duration: 0.3s;
}

html,
body {
    width: 100%;
    height: 100%;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-dark);
    background-color: var(--color-light);
}

/* ============================================
   Typography
   ============================================ */

h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    margin-bottom: calc(var(--spacing-unit) * 0.5);
    line-height: 1.2;
}

h1 {
    font-size: 2.5rem;
}

h2 {
    font-size: 2rem;
    margin-bottom: var(--spacing-unit);
}

h3 {
    font-size: 1.5rem;
}

p {
    margin-bottom: calc(var(--spacing-unit) * 0.5);
}

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color var(--transition-duration);
}

a:hover {
    color: var(--color-primary);
    text-decoration: underline;
}

/* ============================================
   Layout
   ============================================ */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-unit);
}

#app {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.main {
    flex: 1;
}

/* ============================================
   Header
   ============================================ */

.header {
    background: linear-gradient(135deg, var(--color-primary) 0%, #1e40af 100%);
    color: white;
    padding: calc(var(--spacing-unit) * 3) 0;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

.header h1 {
    margin-bottom: calc(var(--spacing-unit) * 0.25);
}

.subtitle {
    font-size: 1.25rem;
    opacity: 0.95;
    margin: 0;
}

/* ============================================
   Sections
   ============================================ */

section {
    padding: calc(var(--spacing-unit) * 4) 0;
}

section:nth-child(odd) {
    background-color: white;
}

section:nth-child(even) {
    background-color: var(--color-light);
}

/* ============================================
   Hero Section
   ============================================ */

.hero {
    text-align: center;
}

.hero h2 {
    color: var(--color-primary);
    margin-bottom: calc(var(--spacing-unit) * 1.5);
}

.hero p {
    font-size: 1.1rem;
    color: var(--color-gray);
    margin-bottom: calc(var(--spacing-unit) * 2);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* ============================================
   Features Section
   ============================================ */

.features h2 {
    color: var(--color-primary);
    margin-bottom: calc(var(--spacing-unit) * 2);
}

.feature-list {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-unit);
}

.feature-list li {
    padding: var(--spacing-unit);
    background: white;
    border-radius: var(--border-radius);
    border-left: 4px solid var(--color-primary);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    transition: transform var(--transition-duration), box-shadow var(--transition-duration);
}

.feature-list li:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.15);
}

/* ============================================
   Counter Section
   ============================================ */

.counter h2 {
    color: var(--color-primary);
    margin-bottom: calc(var(--spacing-unit) * 2);
}

.counter-box {
    background: white;
    padding: calc(var(--spacing-unit) * 3);
    border-radius: var(--border-radius);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    max-width: 500px;
    margin: 0 auto;
    text-align: center;
}

.counter-box p {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: calc(var(--spacing-unit) * 1.5);
}

#count {
    display: inline-block;
    min-width: 3rem;
    padding: 0.25rem 0.5rem;
    background: var(--color-primary);
    color: white;
    border-radius: 0.25rem;
}

/* ============================================
   Violin Intonation Game Section
   ============================================ */

.violin-game h2 {
    color: var(--color-primary);
    margin-bottom: calc(var(--spacing-unit) * 2);
    text-align: center;
}

.violin-game .container {
    max-width: 500px;
    margin: 0 auto;
    text-align: center;
}

#violinControls button {
    margin: 0 0.5em;
}

#violinResult {
    font-size: 1.3rem;
    font-weight: 600;
    min-height: 2em;
}

/* ============================================
   Replay Controls Section
   ============================================ */

#replayControls {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75em;
    margin-bottom: 1em;
}

#replayControls button {
    margin: 0.2em;
}

/* ============================================
   Buttons
   ============================================ */

.btn {
    padding: calc(var(--spacing-unit) * 0.75) calc(var(--spacing-unit) * 1.5);
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-duration);
    display: inline-block;
}

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

.btn-primary:hover {
    background-color: #2563eb;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.4);
}

.btn-secondary {
    background-color: var(--color-secondary);
    color: white;
    margin: 0 calc(var(--spacing-unit) * 0.5);
}

.btn-secondary:hover {
    background-color: #059669;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.4);
}

.btn-tertiary {
    background-color: var(--color-gray);
    color: white;
    margin: 0 calc(var(--spacing-unit) * 0.5);
}

.btn-tertiary:hover {
    background-color: #4b5563;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(107, 114, 128, 0.4);
}

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

/* ============================================
   Footer
   ============================================ */

.footer {
    background-color: var(--color-dark);
    color: white;
    text-align: center;
    padding: calc(var(--spacing-unit) * 2) 0;
    margin-top: auto;
}

.footer p {
    margin: 0;
}

/* ============================================
   Responsive Design
   ============================================ */

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

    h2 {
        font-size: 1.5rem;
    }

    section {
        padding: calc(var(--spacing-unit) * 2) 0;
    }

    .header {
        padding: calc(var(--spacing-unit) * 2) 0;
    }

    .feature-list {
        grid-template-columns: 1fr;
    }

    .counter-box {
        padding: var(--spacing-unit);
    }

    .btn {
        padding: calc(var(--spacing-unit) * 0.5) var(--spacing-unit);
        font-size: 0.9rem;
    }

    .btn-secondary,
    .btn-tertiary {
        margin: calc(var(--spacing-unit) * 0.25);
    }
}

@media (max-width: 480px) {
    html,
    body {
        font-size: 14px;
    }

    h1 {
        font-size: 1.5rem;
    }

    h2 {
        font-size: 1.25rem;
    }

    .header h1 {
        font-size: 1.75rem;
    }

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