/* Main CSS for Time-First Gravity Blog */

/* Base Styles */
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    margin: 0;
    padding: 0;
    background-color: #fff;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 20px;
}

.wide-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 20px;
}

/* Typography */
h1 {
    color: #2c3e50;
    border-bottom: 3px solid #3498db;
    padding-bottom: 10px;
    margin-bottom: 30px;
}

h2 {
    color: #34495e;
    margin-top: 40px;
    margin-bottom: 20px;
    border-left: 4px solid #3498db;
    padding-left: 15px;
}

h3 {
    color: #34495e;
    margin-top: 30px;
    margin-bottom: 15px;
}

p {
    margin-bottom: 16px;
    text-align: justify;
}

strong {
    color: #2c3e50;
}

/* Navigation Bar */
.navbar {
    background-color: #2c3e50;
    padding: 0;
    margin: 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

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

.nav-brand {
    color: white;
    text-decoration: none;
    font-weight: 600;
    font-size: 1.2em;
    padding: 15px 0;
}

.nav-menu {
    display: flex;
    list-style: none;
    margin: 0;
    padding: 0;
}

.nav-item {
    position: relative;
}

.nav-link {
    color: white;
    text-decoration: none;
    padding: 15px 20px;
    display: block;
}

.nav-link:hover {
    background-color: #34495e;
}

/* Dropdown Menu */
.dropdown {
    position: absolute;
    top: 100%;
    left: 0;
    background-color: #34495e;
    min-width: 250px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.2);
    display: none;
}

.nav-item:hover .dropdown {
    display: block;
}

.dropdown-item {
    color: white;
    text-decoration: none;
    padding: 12px 20px;
    display: block;
    border-bottom: 1px solid rgba(255,255,255,0.1);
}

.dropdown-item:hover {
    background-color: #2c3e50;
}

/* Breadcrumbs */
.breadcrumbs {
    padding: 10px 0;
    margin-bottom: 20px;
    font-size: 0.9em;
    color: #7f8c8d;
}

.breadcrumbs a {
    color: #3498db;
    text-decoration: none;
    margin: 0 5px;
}

.breadcrumbs a:hover {
    text-decoration: underline;
}

/* View Toggle */
.view-toggle {
    display: inline-flex;
    border: 2px solid #3498db;
    border-radius: 5px;
    overflow: hidden;
    margin: 20px 0;
}

.view-toggle a {
    padding: 10px 20px;
    text-decoration: none;
    color: #3498db;
    background-color: white;
}

.view-toggle a.active {
    background-color: #3498db;
    color: white;
}

.view-toggle a:hover:not(.active) {
    background-color: #ecf8ff;
}

/* Paper Cards */
.papers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 20px;
    margin: 30px 0;
}

.paper-card {
    background-color: #f8f9fa;
    border-radius: 8px;
    padding: 20px;
    border: 1px solid #e1e8ed;
}

.paper-link-text {
    color: #3498db;
    text-decoration: none;
    font-weight: 500;
    display: inline-block;
    margin-top: 10px;
}

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

.paper-links {
    margin-top: 12px;
}

.paper-card h3 {
    margin-top: 0;
    color: #2c3e50;
    border-bottom: 2px solid #3498db;
    padding-bottom: 10px;
}

.paper-meta {
    font-size: 0.85em;
    color: #7f8c8d;
    margin: 10px 0;
}

.paper-description {
    margin: 15px 0;
    line-height: 1.5;
}

.paper-buttons {
    display: flex;
    gap: 10px;
    margin-top: 15px;
}

.btn {
    padding: 10px 20px;
    text-decoration: none;
    border-radius: 5px;
    display: inline-block;
    text-align: center;
    flex: 1;
}

.btn-primary,
.btn-secondary {
    background-color: white;
    color: #3498db;
    border: 2px solid #3498db;
}

.btn-primary:hover,
.btn-secondary:hover {
    background-color: #f0f8ff;
}

/* Step-by-step Navigation */
.step-nav-container {
    display: flex;
    gap: 30px;
    margin-top: 20px;
    max-width: 1200px;
    margin-left: auto;
    margin-right: auto;
}

.step-sidebar {
    width: 220px;
    flex-shrink: 0;
    background-color: #f8f9fa;
    border-radius: 8px;
    padding: 20px;
    height: fit-content;
    position: sticky;
    top: 70px;
}

.step-content {
    flex: 1;
    min-width: 0;
    max-width: 900px;
}

.step-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.step-list li {
    margin-bottom: 10px;
}

.step-list a {
    color: #333;
    text-decoration: none;
    display: block;
    padding: 8px 12px;
    border-radius: 5px;
}

.step-list a:hover {
    background-color: #e3f2fd;
    color: #2980b9;
}

.step-list a.active {
    background-color: #3498db;
    color: white;
}

/* Chapter Navigation */
.chapter-nav {
    display: flex;
    justify-content: space-between;
    margin: 40px 0;
    padding-top: 20px;
    border-top: 1px solid #e1e8ed;
}

.chapter-nav a {
    text-decoration: none;
    color: #3498db;
    padding: 10px 20px;
    border: 2px solid #3498db;
    border-radius: 5px;
}

.chapter-nav a:hover {
    background-color: #3498db;
    color: white;
}

.chapter-nav .placeholder {
    visibility: hidden;
}

/* Mathematical Content */
.math {
    font-family: 'Times New Roman', serif;
    font-style: italic;
    font-size: 1.1em;
    text-align: center;
    margin: 20px 0;
    padding: 10px;
    background-color: #f8f9fa;
    border-radius: 5px;
}

/* Tables */
table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
    font-size: 0.95em;
}

th, td {
    padding: 12px;
    text-align: left;
    border: 1px solid #ddd;
}

th {
    background-color: #f8f9fa;
    font-weight: 600;
    color: #2c3e50;
}

tr:nth-child(even) {
    background-color: #f9f9f9;
}

tr:hover {
    background-color: #f5f5f5;
}

/* Highlight Boxes */
.highlight {
    background-color: #ecf0f1;
    padding: 15px;
    border-radius: 5px;
    margin: 20px 0;
    border-left: 4px solid #e74c3c;
}

.highlight.info {
    border-left-color: #3498db;
}

.highlight.success {
    border-left-color: #2ecc71;
}

/* Lists */
ol, ul {
    margin-bottom: 16px;
    padding-left: 30px;
}

li {
    margin-bottom: 8px;
}

/* Footer */
.footer {
    margin-top: 50px;
    padding-top: 20px;
    border-top: 1px solid #bdc3c7;
    text-align: center;
    color: #7f8c8d;
    font-size: 0.9em;
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
    .nav-container {
        flex-direction: column;
        padding: 0;
    }
    
    .nav-menu {
        width: 100%;
        flex-direction: column;
    }
    
    .nav-item {
        width: 100%;
    }
    
    .dropdown {
        position: static;
        width: 100%;
        box-shadow: none;
        background-color: #445a75;
    }
    
    .papers-grid {
        grid-template-columns: 1fr;
    }
    
    .step-nav-container {
        flex-direction: column;
    }
    
    .step-sidebar {
        width: 100%;
        position: static;
        margin-bottom: 20px;
    }
    
    .paper-buttons {
        flex-direction: column;
    }
}

@media (max-width: 600px) {
    body {
        font-size: 0.95em;
    }
    
    .container {
        padding: 15px;
    }
    
    h1 {
        font-size: 1.8em;
    }
    
    h2 {
        font-size: 1.3em;
    }
    
    .chapter-nav {
        flex-direction: column;
        gap: 10px;
    }
    
    .chapter-nav a {
        width: 100%;
        text-align: center;
    }
}