* {
    box-sizing: border-box;
}

body {
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    color: #2c3e50;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    min-height: 100vh;
    margin: 0;
    transition: background 0.3s ease, color 0.3s ease;
}

body.dark {
    background: linear-gradient(135deg, #1e1e2e 0%, #2d2d44 100%);
    color: #e8e8e8;
}

a {
    cursor: pointer;
    text-decoration: none;
    transition: color 0.3s ease, opacity 0.3s ease;
}

a:hover {
    opacity: 0.8;
}

hr {
    margin: 20px 0;
    border: none;
    border-top: 1px solid rgba(0, 0, 0, 0.1);
}

body.dark hr {
    border-top-color: rgba(255, 255, 255, 0.1);
}

.navbar {
    margin-bottom: 0;
    min-height: 60px;
    border: none;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    transition: all 0.3s ease;
}

.navbar-default {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
}

.navbar-default .navbar-nav > li > a {
    color: #34495e;
    font-weight: 500;
    transition: all 0.3s ease;
    padding: 20px 15px;
}

.navbar-default .navbar-nav > li > a:hover {
    color: #3498db;
    background: rgba(52, 152, 219, 0.05);
}

.navbar-default .navbar-nav > .active > a {
    background: rgba(52, 152, 219, 0.1);
    color: #3498db;
    border-bottom: 3px solid #3498db;
    padding-bottom: 17px;
}

body.dark .navbar-default {
    background: rgba(30, 30, 46, 0.95);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

body.dark .navbar-default .navbar-nav > li > a {
    color: #b8c4ce;
}

body.dark .navbar-default .navbar-nav > .active > a {
    background: rgba(100, 149, 237, 0.1);
    color: #6495ed;
    border-bottom-color: #6495ed;
}

body.dark .navbar-default .navbar-nav > li > a:hover {
    color: #ffffff;
    background: rgba(255, 255, 255, 0.05);
}

.navbar-brand {
    padding: 10px 15px;
}

.navbar-brand h1 {
    margin: 0;
    padding: 0;
    color: #2c3e50;
    font-size: 28px;
    font-weight: 700;
    letter-spacing: -0.5px;
    transition: color 0.3s ease;
}

.navbar-brand:hover h1 {
    color: #3498db;
}

body.dark .navbar-brand h1 {
    color: #e8e8e8;
}

body.dark .navbar-brand:hover h1 {
    color: #6495ed;
}

.main-container {
    padding-top: 20px;
    padding-bottom: 20px;
}

#timelines {
    padding-top: 20px;
}

.timeline {
    padding: 40px 0;
    margin: 0 auto;
}

.timeline-body {
    color: #2c3e50;
    padding: 0;
    margin-top: 20px;
}

body.dark .timeline-body {
    color: #e8e8e8;
}

.timeline-era {
    background: rgba(255, 255, 255, 0.95);
    padding: 15px;
    margin-bottom: 20px;
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
}

.timeline-era:hover {
    box-shadow: 0 6px 30px rgba(0, 0, 0, 0.12);
    transform: translateY(-2px);
}

body.dark .timeline-era {
    background: rgba(30, 30, 46, 0.95);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

body.dark .timeline-era:hover {
    box-shadow: 0 6px 30px rgba(0, 0, 0, 0.5);
}

.timeline-body h2 {
    color: #2c3e50;
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 20px;
    letter-spacing: -0.5px;
}

body.dark .timeline-body h2 {
    color: #e8e8e8;
}

.timeline-era h4 {
    font-weight: 700;
    font-size: 20px;
    margin: 0 0 15px;
    color: #34495e;
    border-left: 4px solid #3498db;
    padding: 15px;
    background: linear-gradient(135deg, rgba(52, 152, 219, 0.25), rgba(41, 128, 185, 0.15));
    border-radius: 8px;
}

.timeline-era h4 .era-time {
    display: inline-block;
    font-size: 14px;
    font-weight: 500;
    background: linear-gradient(135deg, #3498db, #2980b9);
    color: white;
    padding: 4px 12px;
    border-radius: 16px;
    white-space: nowrap;
    box-shadow: 0 2px 8px rgba(52, 152, 219, 0.3);
    letter-spacing: 0.5px;
    font-style: normal;
    margin-top: 8px;
}

body.dark .timeline-era h4 {
    color: #b8c4ce;
    border-left-color: #6495ed;
    background: linear-gradient(135deg, rgba(100, 149, 237, 0.35), rgba(90, 127, 216, 0.25));
}

body.dark .timeline-era h4 .era-time {
    background: linear-gradient(135deg, #6495ed, #5a7fd8);
    box-shadow: 0 2px 8px rgba(100, 149, 237, 0.3);
}

.timeline-era p {
    line-height: 1.8;
    margin-bottom: 15px;
    font-size: 16px;
}

.timeline-era ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.timeline-era li {
    clear: both;
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 8px;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.timeline-era li:nth-child(2n) {
    background: linear-gradient(135deg, rgba(52, 152, 219, 0.05) 0%, rgba(52, 152, 219, 0.02) 100%);
    border-left: 3px solid rgba(52, 152, 219, 0.3);
}

.timeline-era li:nth-child(2n+1) {
    background: linear-gradient(135deg, rgba(155, 89, 182, 0.05) 0%, rgba(155, 89, 182, 0.02) 100%);
    border-left: 3px solid rgba(155, 89, 182, 0.3);
}

body.dark .timeline-era li:nth-child(2n) {
    background: linear-gradient(135deg, rgba(100, 149, 237, 0.1) 0%, rgba(100, 149, 237, 0.05) 100%);
    border-left-color: rgba(100, 149, 237, 0.5);
}

body.dark .timeline-era li:nth-child(2n+1) {
    background: linear-gradient(135deg, rgba(147, 112, 219, 0.1) 0%, rgba(147, 112, 219, 0.05) 100%);
    border-left-color: rgba(147, 112, 219, 0.5);
}

.timeline-era li:hover {
    transform: translateX(5px);
    box-shadow: 0 3px 15px rgba(0, 0, 0, 0.1);
}

body.dark .timeline-era li:hover {
    box-shadow: 0 3px 15px rgba(0, 0, 0, 0.3);
}

.timeline-era li img {
    float: left;
    margin-right: 15px;
    margin-bottom: 10px;
    border-radius: 6px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease;
}

/* Two-column layout for wide screens */
@media (min-width: 992px) {
    .timeline-era li {
        display: flex;
        align-items: flex-start;
        gap: 20px;
    }

    .timeline-era li img {
        float: none;
        margin-right: 0;
        margin-bottom: 0;
        max-width: 250px;
        height: auto;
    }

    .timeline-era li a:first-child {
        flex-shrink: 0;
    }

    .timeline-era li .event-content {
        flex-grow: 1;
        min-width: 0;
    }

    .timeline-era li br:last-of-type {
        display: none;
    }
}

.timeline-era li img:hover {
    transform: scale(1.05);
}

.timeline-era li a {
    font-style: italic;
    font-size: 13px;
    color: #3498db;
    transition: all 0.3s ease;
    display: inline-block;
    margin-top: 5px;
}

.timeline-era li a:hover {
    color: #2980b9;
    transform: translateX(3px);
}

body.dark .timeline-era li a {
    color: #6495ed;
}

body.dark .timeline-era li a:hover {
    color: #87a9ff;
}

.timeline-era li span {
    display: block;
    margin-top: 5px;
    margin-bottom: 8px;
}

.timeline-era li b {
    font-weight: 600;
    color: #2c3e50;
    font-size: 16px;
}

body.dark .timeline-era li b {
    color: #e8e8e8;
}

.timeline-era hr {
    margin: 35px 0;
    border: none;
    border-top: 2px solid rgba(52, 152, 219, 0.1);
}

body.dark .timeline-era hr {
    border-top-color: rgba(100, 149, 237, 0.2);
}

.head {
    position: relative;
    padding: 0;
}

.head h2 {
    color: #2c3e50;
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 20px;
    letter-spacing: -0.5px;
    position: relative;
    display: inline-block;
}

.head h2:after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    width: 60px;
    height: 4px;
    background: linear-gradient(90deg, #3498db 0%, rgba(52, 152, 219, 0) 100%);
    border-radius: 2px;
}

body.dark .head h2 {
    color: #e8e8e8;
}

body.dark .head h2:after {
    background: linear-gradient(90deg, #6495ed 0%, rgba(100, 149, 237, 0) 100%);
}

.head p {
    margin-top: 20px;
    font-size: 16px;
    line-height: 1.6;
}

.head p a {
    color: #3498db;
    font-weight: 500;
    transition: all 0.3s ease;
}

.head p a:hover {
    color: #2980b9;
}

body.dark .head p a {
    color: #6495ed;
}

body.dark .head p a:hover {
    color: #87a9ff;
}

.sources {
    font-style: italic;
    font-size: 14px;
    padding: 15px;
    background: rgba(52, 152, 219, 0.05);
    border-radius: 8px;
    margin-top: 20px;
    border-left: 3px solid rgba(52, 152, 219, 0.3);
}

body.dark .sources {
    background: rgba(100, 149, 237, 0.1);
    border-left-color: rgba(100, 149, 237, 0.5);
}

.navbar-toggle {
    border: 1px solid rgba(0, 0, 0, 0.1);
    margin-top: 12px;
}

.navbar-toggle .icon-bar {
    background: #34495e;
}

body.dark .navbar-toggle {
    border-color: rgba(255, 255, 255, 0.1);
}

body.dark .navbar-toggle .icon-bar {
    background: #b8c4ce;
}

#dark-mode {
    font-size: 18px;
}

#dark-mode .glyphicon {
    transition: transform 0.3s ease;
}

#dark-mode:hover .glyphicon {
    transform: rotate(180deg);
}

@media (max-width: 768px) {
    .navbar-brand h1 {
        font-size: 24px;
    }

    .head h2 {
        font-size: 28px;
    }

    .timeline-body {
        padding: 0;
    }

    .timeline-body h2 {
        font-size: 24px;
    }

    .timeline-body h4 {
        font-size: 24px;
    }

    .timeline-era li {
        padding: 5px;
    }
}

@media (min-width: 992px) {
    .sources {
        position: absolute;
        right: 0;
        top: 30px;
        text-align: right;
        max-width: 300px;
        margin-top: 0;
    }

    .sources p {
        margin: 0;
    }
}

.sources a {
    cursor: pointer;
    color: #3498db;
    font-weight: 500;
}

.sources a:hover {
    color: #2980b9;
}

body.dark .sources a {
    color: #6495ed;
}

body.dark .sources a:hover {
    color: #87a9ff;
}

/* Era Navigation Sidebar */
.era-navigation {
    position: fixed;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
    background: rgba(255, 255, 255, 0.98);
    border-radius: 12px;
    padding: 20px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    z-index: 1000;
    max-height: 70vh;
    overflow-y: auto;
    min-width: 200px;
    max-width: 250px;
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
}

.era-navigation:hover {
    box-shadow: 0 6px 30px rgba(0, 0, 0, 0.15);
}

body.dark .era-navigation {
    background: rgba(30, 30, 46, 0.98);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.4);
}

body.dark .era-navigation:hover {
    box-shadow: 0 6px 30px rgba(0, 0, 0, 0.6);
}

.era-nav-header {
    font-weight: 700;
    font-size: 16px;
    margin-bottom: 15px;
    color: #2c3e50;
    padding-bottom: 10px;
    border-bottom: 2px solid rgba(52, 152, 219, 0.2);
}

body.dark .era-nav-header {
    color: #e8e8e8;
    border-bottom-color: rgba(100, 149, 237, 0.3);
}

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

.era-nav-list li {
    margin-bottom: 8px;
}

.era-nav-list a {
    display: block;
    padding: 8px 12px;
    border-radius: 6px;
    color: #34495e;
    transition: all 0.3s ease;
    border-left: 3px solid transparent;
}

.era-nav-list a:hover {
    background: rgba(52, 152, 219, 0.1);
    border-left-color: #3498db;
    transform: translateX(3px);
}

.era-nav-list a.active {
    background: rgba(52, 152, 219, 0.15);
    border-left-color: #3498db;
    color: #2980b9;
    font-weight: 600;
}

body.dark .era-nav-list a {
    color: #b8c4ce;
}

body.dark .era-nav-list a:hover {
    background: rgba(100, 149, 237, 0.15);
    border-left-color: #6495ed;
}

body.dark .era-nav-list a.active {
    background: rgba(100, 149, 237, 0.2);
    border-left-color: #6495ed;
    color: #87a9ff;
}

.era-nav-name {
    display: block;
    font-weight: 500;
    font-size: 14px;
    line-height: 1.3;
}

.era-nav-label {
    display: block;
    font-size: 11px;
    opacity: 0.7;
    margin-top: 2px;
}

/* Mobile adjustments */
@media (max-width: 1200px) {
    .era-navigation {
        right: 10px;
        max-width: 180px;
        min-width: 150px;
        padding: 15px;
    }

    .era-nav-header {
        font-size: 14px;
    }

    .era-nav-name {
        font-size: 12px;
    }

    .era-nav-label {
        font-size: 10px;
    }
}

@media (max-width: 768px) {
    .era-navigation {
        position: fixed;
        right: auto;
        left: 50%;
        top: auto;
        bottom: 20px;
        transform: translateX(-50%);
        max-width: 90%;
        width: auto;
        max-height: 200px;
        flex-direction: row;
    }

    .era-nav-list {
        display: flex;
        flex-wrap: nowrap;
        overflow-x: auto;
        gap: 10px;
    }

    .era-nav-list li {
        flex-shrink: 0;
        margin-bottom: 0;
    }

    .era-nav-list a {
        white-space: nowrap;
    }
}

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

.timeline-era {
    animation: fadeIn 0.6s ease-out;
}

@media (prefers-reduced-motion: reduce) {
    * {
        animation: none !important;
        transition: none !important;
    }
}