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

:root {
    --primary: #4361ee;
    --secondary: #3a0ca3;
    --accent: #4cc9f0;
    --light: #f8f9fa;
    --dark: #212529;
    --success: #4CAF50;
    --warning: #ff9800;
    --danger: #f44336;
    --gray: #6c757d;
    --light-gray: #e9ecef;
    --shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    --radius: 12px;
    --transition: all 0.3s ease;
}

body {
    font-family: 'Poppins', sans-serif;
    line-height: 1.6;
    color: var(--dark);
    background-color: #f5f7ff;
    overflow-x: hidden;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Navigation */
.navbar {
    background: white;
    box-shadow: var(--shadow);
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 1rem 0;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.5rem;
    color: var(--primary);
}

.logo i {
    font-size: 2rem;
}

.nav-links {
    display: flex;
    gap: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--dark);
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: var(--radius);
    transition: var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
    background: var(--primary);
    color: white;
}

.menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--primary);
    cursor: pointer;
}

/* Hero Section */
.hero {
    padding: 4rem 0;
    background: linear-gradient(135deg, #4361ee 0%, #3a0ca3 100%);
    color: white;
}

.hero-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.hero-content h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
    line-height: 1.2;
}

.hero-content p {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

.cta-button {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    background: white;
    color: var(--primary);
    padding: 1rem 2rem;
    border-radius: var(--radius);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
    box-shadow: var(--shadow);
}

.cta-button:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.2);
}

.hero-image img {
    width: 100%;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

/* Features Section */
.features {
    padding: 5rem 0;
    background: white;
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--dark);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

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

.feature-card:hover {
    transform: translateY(-10px);
    border-color: var(--primary);
}

.feature-icon {
    font-size: 3rem;
    color: var(--primary);
    margin-bottom: 1rem;
}

.feature-card h3 {
    margin-bottom: 1rem;
    color: var(--dark);
}

/* How to Use Section */
.how-to-use {
    padding: 5rem 0;
    background: var(--light-gray);
}

.steps {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 2rem;
    text-align: center;
}

.step {
    padding: 2rem;
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    position: relative;
}

.step-number {
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    width: 40px;
    height: 40px;
    background: var(--primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
}

/* Footer */
.footer {
    background: var(--dark);
    color: white;
    padding: 3rem 0 1rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 3rem;
    margin-bottom: 2rem;
}

.footer-logo {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.footer-logo i {
    font-size: 2.5rem;
    color: var(--accent);
    margin-bottom: 1rem;
}

.footer-links {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.footer-links a {
    color: white;
    text-decoration: none;
    opacity: 0.8;
    transition: var(--transition);
}

.footer-links a:hover {
    opacity: 1;
    color: var(--accent);
}

.footer-contact p {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 1rem;
    opacity: 0.8;
}

.social-icons {
    display: flex;
    gap: 1rem;
    margin-top: 1rem;
}

.social-icons a {
    color: white;
    font-size: 1.2rem;
    transition: var(--transition);
}

.social-icons a:hover {
    color: var(--accent);
    transform: translateY(-3px);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    opacity: 0.7;
}

/* Papers Page Styles */
.papers-container {
    padding: 2rem 0;
    min-height: calc(100vh - 200px);
}

.page-header {
    text-align: center;
    margin-bottom: 3rem;
    padding: 2rem;
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.page-header h1 {
    color: var(--primary);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
}

/* Selection Panel */
.selection-panel {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-bottom: 3rem;
}

.selection-card {
    background: white;
    padding: 2rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.selection-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 1.5rem;
    color: var(--primary);
}

.class-options,
.medium-options {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.class-option,
.medium-option,
.subject-option {
    padding: 1rem;
    border: 2px solid var(--light-gray);
    background: white;
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
    font-weight: 500;
    text-align: center;
}

.class-option:hover,
.medium-option:hover,
.subject-option:hover {
    border-color: var(--primary);
    background: #f0f4ff;
}

.class-option.active,
.medium-option.active,
.subject-option.active {
    background: var(--primary);
    color: white;
    border-color: var(--primary);
}

.subject-options {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    gap: 1rem;
}

/* Papers Display */
.papers-display {
    margin-bottom: 3rem;
}

#selectedInfo {
    font-size: 1rem;
    color: var(--gray);
    font-weight: normal;
}

.papers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
}

.paper-card {
    background: white;
    border-radius: var(--radius);
    padding: 1.5rem;
    box-shadow: var(--shadow);
    transition: var(--transition);
    border: 2px solid transparent;
}

.paper-card:hover {
    transform: translateY(-5px);
    border-color: var(--primary);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
}

.paper-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 1rem;
}

.paper-year {
    background: var(--primary);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
}

.paper-subject {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--dark);
    margin-bottom: 0.5rem;
}

.paper-details {
    color: var(--gray);
    font-size: 0.9rem;
    margin-bottom: 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
}

.download-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    width: 100%;
    padding: 0.8rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: var(--radius);
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

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

.no-selection {
    grid-column: 1 / -1;
    text-align: center;
    padding: 4rem;
    background: white;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.no-selection i {
    font-size: 4rem;
    color: var(--light-gray);
    margin-bottom: 1rem;
}

/* Info Section */
.info-section {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-top: 3rem;
}

.info-card {
    background: white;
    padding: 2rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.info-card i {
    font-size: 2.5rem;
    color: var(--primary);
    margin-bottom: 1rem;
}

.info-card h3 {
    margin-bottom: 1rem;
    color: var(--dark);
}

.info-card ul {
    list-style: none;
    padding-left: 0;
}

.info-card li {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--light-gray);
}

.info-card li:last-child {
    border-bottom: none;
}

/* Responsive Design */
@media (max-width: 992px) {
    .hero-container {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero-content h1 {
        font-size: 2.5rem;
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 1rem;
        box-shadow: var(--shadow);
    }
    
    .nav-links.active {
        display: flex;
    }
    
    .menu-toggle {
        display: block;
    }
    
    .class-options,
    .medium-options {
        grid-template-columns: 1fr;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .hero-content h1 {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 15px;
    }
    
    .feature-card,
    .selection-card,
    .paper-card {
        padding: 1.5rem;
    }
    
    .step {
        padding: 1.5rem;
    }
  }