/* ===== RESET & BASE STYLES ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Color Palette */
    --primary-blue: #2563eb;
    --primary-blue-dark: #1d4ed8;
    --primary-blue-light: #dbeafe;
    --secondary-color: #10b981;
    --text-dark: #1f2937;
    --text-light: #6b7280;
    --bg-white: #ffffff;
    --bg-light: #f9fafb;
    --border-color: #e5e7eb;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-full: 9999px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    line-height: 1.5;
    color: var(--text-dark);
    background-color: var(--bg-light);
}

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

/* ===== HEADER STYLES ===== */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--bg-white);
    box-shadow: var(--shadow-md);
    backdrop-filter: blur(10px);
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) 0;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    text-decoration: none;
}

.logo-icon {
    color: var(--primary-blue);
    font-size: 1.5rem;
}

.logo-text {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-dark);
}

.logo-highlight {
    color: var(--primary-blue);
}

.nav-menu {
    display: flex;
    gap: var(--spacing-lg);
    list-style: none;
}

.nav-link {
    text-decoration: none;
    color: var(--text-light);
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-md);
    transition: all 0.2s ease;
    position: relative;
}

.nav-link:hover {
    color: var(--primary-blue);
    background-color: var(--primary-blue-light);
}

.nav-link.active {
    color: var(--primary-blue);
    font-weight: 600;
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 50%;
    transform: translateX(-50%);
    width: 20px;
    height: 3px;
    background-color: var(--primary-blue);
    border-radius: var(--radius-full);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

/* ===== BUTTON STYLES ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 500;
    text-decoration: none;
    cursor: pointer;
    border: none;
    transition: all 0.2s ease;
    gap: 0.5rem;
    font-size: 0.95rem;
}

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

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

.btn-secondary {
    background-color: white;
    color: var(--primary-blue);
    border: 2px solid var(--primary-blue);
}

.btn-secondary:hover {
    background-color: var(--primary-blue-light);
    transform: translateY(-2px);
}

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.1rem;
}

.btn-full-width {
    width: 100%;
}

.btn-icon {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

/* ===== HERO SECTION ===== */
.hero {
    padding: var(--spacing-xl) 0;
    background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 50%;
    height: 100%;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" preserveAspectRatio="none"><path fill="%232563eb" opacity="0.1" d="M0,0 L100,0 L100,100 Q50,80 0,100 Z"/></svg>');
    background-size: cover;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 600px;
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-md);
    color: var(--text-dark);
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-light);
    margin-bottom: var(--spacing-lg);
    line-height: 1.6;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

/* ===== SUBJECTS SECTION ===== */
.subjects-section {
    padding: var(--spacing-xl) 0;
    background-color: var(--bg-white);
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xl);
    color: var(--text-dark);
}

.subjects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-xl);
}

.subject-card {
    background: var(--bg-white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
    text-align: center;
}

.subject-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-blue);
}

.subject-icon {
    font-size: 2.5rem;
    color: var(--primary-blue);
    margin-bottom: var(--spacing-sm);
}

.subject-name {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: var(--spacing-xs);
}

.subject-desc {
    color: var(--text-light);
    font-size: 0.95rem;
}

/* ===== CTA SECTION ===== */
.cta-section {
    padding: var(--spacing-xl) 0;
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-blue-dark) 100%);
    color: white;
    text-align: center;
    border-radius: var(--radius-lg);
    margin: var(--spacing-xl) 0;
}

.cta-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

.cta-description {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-lg);
    opacity: 0.9;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.cta-button {
    background-color: white;
    color: var(--primary-blue);
    font-weight: 600;
    padding: 1rem 3rem;
    font-size: 1.1rem;
}

.cta-button:hover {
    background-color: var(--bg-light);
    transform: scale(1.05);
}

/* ===== FEATURES SECTION ===== */
.features-section {
    padding: var(--spacing-xl) 0;
    background-color: var(--bg-light);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

.feature-card {
    background: var(--bg-white);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    text-align: center;
}

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

.feature-title {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--text-dark);
}

.feature-desc {
    color: var(--text-light);
    line-height: 1.6;
}

/* ===== DASHBOARD STYLES ===== */
.dashboard {
    min-height: calc(100vh - 80px);
    padding: var(--spacing-xl) 0;
}

.dashboard-header {
    margin-bottom: var(--spacing-xl);
}

.dashboard-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-dark);
    margin-bottom: var(--spacing-xs);
}

.dashboard-subtitle {
    color: var(--text-light);
    font-size: 1.1rem;
}

.notes-card {
    background: var(--bg-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    max-width: 800px;
    margin: 0 auto;
}

.notes-header {
    padding: var(--spacing-lg);
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-blue-dark) 100%);
    color: white;
}

.notes-title {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
}

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

.notes-content {
    padding: var(--spacing-lg);
}

.notes-description {
    color: var(--text-light);
    line-height: 1.6;
    margin-bottom: var(--spacing-lg);
}

.notes-features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.feature-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--text-dark);
}

.feature-item i {
    color: var(--primary-blue);
    font-size: 1.25rem;
}

.notes-actions {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

/* ===== PURCHASE PAGE ===== */
.purchase-section {
    padding: var(--spacing-xl) 0;
    min-height: calc(100vh - 80px);
}

.purchase-card {
    background: var(--bg-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: var(--spacing-xl);
    max-width: 800px;
    margin: 0 auto;
}

.purchase-header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.purchase-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-dark);
    margin-bottom: var(--spacing-sm);
}

.purchase-subtitle {
    color: var(--text-light);
    font-size: 1.1rem;
}

.pricing-card {
    background: var(--bg-light);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    border: 2px solid var(--primary-blue);
}

.price-amount {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-blue);
    text-align: center;
    margin-bottom: var(--spacing-sm);
}

.price-period {
    text-align: center;
    color: var(--text-light);
    margin-bottom: var(--spacing-lg);
}

.purchase-features {
    margin-bottom: var(--spacing-lg);
}

.feature-list {
    list-style: none;
}

.feature-list li {
    padding: var(--spacing-sm) 0;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.feature-list li:last-child {
    border-bottom: none;
}

.feature-list i {
    color: var(--secondary-color);
}

/* ===== FOOTER ===== */
.footer {
    background-color: var(--text-dark);
    color: white;
    padding: var(--spacing-xl) 0;
    margin-top: var(--spacing-xl);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-lg);
}

.footer-logo {
    font-size: 1.5rem;
    font-weight: 700;
}

.footer-links {
    display: flex;
    gap: var(--spacing-lg);
}

.footer-link {
    color: rgba(255, 255, 255, 0.8);
    text-decoration: none;
    transition: color 0.2s ease;
}

.footer-link:hover {
    color: white;
}

.copyright {
    width: 100%;
    text-align: center;
    margin-top: var(--spacing-lg);
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.9rem;
}

/* ===== AUTH PAGES ===== */
.auth-section {
    min-height: calc(100vh - 80px);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-xl) 0;
}

.auth-card {
    background: var(--bg-white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: var(--spacing-xl);
    width: 100%;
    max-width: 450px;
}

.auth-title {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-sm);
    color: var(--text-dark);
}

.auth-subtitle {
    text-align: center;
    color: var(--text-light);
    margin-bottom: var(--spacing-lg);
}

.auth-form {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.form-label {
    font-weight: 500;
    color: var(--text-dark);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.form-input {
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    transition: all 0.2s ease;
}

.form-input:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.auth-footer {
    text-align: center;
    margin-top: var(--spacing-lg);
    color: var(--text-light);
}

.auth-link {
    color: var(--primary-blue);
    text-decoration: none;
    font-weight: 500;
}

.auth-link:hover {
    text-decoration: underline;
}

/* ===== UTILITY CLASSES ===== */
.text-center { text-align: center; }
.mb-sm { margin-bottom: var(--spacing-sm); }
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }
.mb-xl { margin-bottom: var(--spacing-xl); }
.mt-sm { margin-top: var(--spacing-sm); }
.mt-md { margin-top: var(--spacing-md); }
.mt-lg { margin-top: var(--spacing-lg); }
.mt-xl { margin-top: var(--spacing-xl); }
.hidden { display: none !important; }

/* ===== RESPONSIVE DESIGN ===== */
@media (max-width: 768px) {
    .hero-title {
        font-size: 2.5rem;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .cta-title {
        font-size: 2rem;
    }
    
    .navbar {
        flex-direction: column;
        gap: var(--spacing-sm);
        padding: var(--spacing-sm);
    }
    
    .nav-menu {
        gap: var(--spacing-sm);
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .notes-actions {
        flex-direction: column;
    }
    
    .footer-content {
        flex-direction: column;
        text-align: center;
    }
    
    .footer-links {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .hero-subtitle {
        font-size: 1.1rem;
    }
    
    .auth-card {
        padding: var(--spacing-lg);
    }
    
    .purchase-card {
        padding: var(--spacing-lg);
    }
}