/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #48bb78;
    --primary-dark: #38a169;
    --secondary-color: #2f855a;
    --success-color: #48bb78;
    --error-color: #f56565;
    --text-primary: #2d3748;
    --text-secondary: #718096;
    --bg-light: #f7fafc;
    --bg-white: #ffffff;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    color: var(--text-primary);
    background: linear-gradient(135deg, #48bb78 0%, #2f855a 100%);
    min-height: 100vh;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
}

header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 20px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo h1 {
    font-size: 1.5rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

nav {
    display: flex;
    gap: 2rem;
}

nav a {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    padding: 0.5rem 0;
    border-bottom: 2px solid transparent;
}

nav a:hover {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

/* Hero Section */
.hero {
    text-align: center;
    padding: 3rem 0 2rem;
    color: white;
}

.hero h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    font-weight: 700;
}

.hero p {
    font-size: 1.2rem;
    opacity: 0.95;
}

/* Main Content */
main {
    padding: 2rem 20px;
}

/* Download Card */
.download-card {
    background: var(--bg-white);
    border-radius: 20px;
    padding: 2.5rem;
    box-shadow: var(--shadow-xl);
    margin-bottom: 3rem;
}

.input-section {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
}

#videoUrl {
    flex: 1;
    padding: 1rem 1.5rem;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    font-size: 1rem;
    transition: var(--transition);
    outline: none;
}

#videoUrl:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

/* Buttons */
.btn {
    padding: 1rem 2rem;
    border: none;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    justify-content: center;
    white-space: nowrap;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

.btn-download {
    background: var(--success-color);
    color: white;
    width: 100%;
    margin-top: 1.5rem;
    padding: 1.2rem;
    font-size: 1.1rem;
}

.btn-download:hover {
    background: #38a169;
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

/* Spinner */
.spinner {
    width: 20px;
    height: 20px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.hidden {
    display: none !important;
}

/* Error Message */
.error-message {
    background: #fed7d7;
    color: #c53030;
    padding: 1rem 1.5rem;
    border-radius: 12px;
    margin-bottom: 1rem;
    border-left: 4px solid var(--error-color);
}

/* Video Info */
.video-info {
    margin-top: 2rem;
    animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.video-preview {
    display: flex;
    gap: 1.5rem;
    margin-bottom: 2rem;
    padding-bottom: 2rem;
    border-bottom: 2px solid var(--border-color);
}

#videoThumbnail {
    width: 200px;
    height: 112px;
    object-fit: cover;
    border-radius: 12px;
    box-shadow: var(--shadow-md);
}

.video-details {
    flex: 1;
}

.video-details h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.video-meta {
    color: var(--text-secondary);
    font-size: 0.9rem;
    display: flex;
    gap: 1rem;
    margin-bottom: 0.5rem;
}

.platform-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
}

/* Download Options */
.download-options {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-bottom: 1rem;
}

.option-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.option-group label {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.9rem;
}

select {
    padding: 0.75rem 1rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    background: white;
    cursor: pointer;
    transition: var(--transition);
    outline: none;
}

select:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.subtitle-info {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1rem;
    background: var(--bg-light);
    border-radius: 8px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Features Section */
.features {
    margin: 4rem 0;
}

.features h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: white;
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
}

.feature-card {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: 16px;
    text-align: center;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.feature-card p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* How to Use Section */
.how-to {
    margin: 4rem 0;
}

.how-to h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: white;
}

.steps {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 2rem;
}

.step {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: 16px;
    text-align: center;
    position: relative;
}

.step-number {
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: bold;
    margin: 0 auto 1rem;
}

.step h3 {
    margin-bottom: 0.5rem;
}

.step p {
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Supported Platforms */
.supported-platforms {
    margin: 4rem 0;
}

.supported-platforms h2 {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: white;
}

.platforms-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.platform {
    background: var(--bg-white);
    padding: 1.5rem;
    border-radius: 12px;
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    transition: var(--transition);
}

.platform:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.platform-icon {
    width: 60px;
    height: 60px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.8rem;
    color: white;
    font-weight: bold;
}

.platform span {
    font-weight: 600;
    color: var(--text-primary);
}

.note {
    text-align: center;
    color: white;
    font-size: 0.9rem;
    background: rgba(255, 255, 255, 0.1);
    padding: 1rem;
    border-radius: 8px;
    backdrop-filter: blur(10px);
}

/* Footer */
footer {
    background: rgba(255, 255, 255, 0.95);
    padding: 2rem 0;
    margin-top: 4rem;
    text-align: center;
}

footer p {
    margin: 0.5rem 0;
}

.disclaimer {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    .hero h2 {
        font-size: 1.8rem;
    }

    .hero p {
        font-size: 1rem;
    }

    .download-card {
        padding: 1.5rem;
    }

    .input-section {
        flex-direction: column;
    }

    .video-preview {
        flex-direction: column;
    }

    #videoThumbnail {
        width: 100%;
        height: auto;
    }

    .features h2,
    .how-to h2,
    .supported-platforms h2 {
        font-size: 2rem;
    }

    nav {
        gap: 1rem;
    }

    nav a {
        font-size: 0.9rem;
    }

    .feature-grid,
    .steps,
    .platforms-grid {
        grid-template-columns: 1fr;
    }

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

@media (max-width: 480px) {
    .logo h1 {
        font-size: 1.2rem;
    }

    header .container {
        flex-direction: column;
        gap: 1rem;
    }

    nav {
        flex-wrap: wrap;
        justify-content: center;
    }

    .hero h2 {
        font-size: 1.5rem;
    }

    .btn {
        padding: 0.875rem 1.5rem;
        font-size: 0.95rem;
    }
}

/* Print Styles */
@media print {
    header,
    footer,
    .download-card,
    .features,
    .how-to,
    .supported-platforms {
        display: none;
    }
}