:root {
    --science-primary: #e74c3c;
    --science-secondary: #ec7063;
    --science-accent: #c0392b;
    --science-gradient: linear-gradient(135deg, #e74c3c, #c0392b);
    --evolution-color: #27ae60;
    --earth-color: #2980b9;
    --astronomy-color: #34495e;
    --genetics-color: #16a085;
    --dating-color: #d35400;
    --human-evolution-color: #e67e22;
    --biblical-perspectives-primary: #6a4c93; /* Deep Purple */
    --biblical-perspectives-secondary: #9c7bb8;
    --biblical-perspectives-accent: #4a2c6a;
    --neutral-dark: #333333;
    --neutral-light: #f5f5f5;
    --neutral-mid: #e0e0e0;
    --box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
    --transition-time: 0.3s;
    --card-border-radius: 16px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

body {
    background-color: var(--neutral-light);
    color: var(--neutral-dark);
    line-height: 1.6;
    overflow-x: hidden;
    width: 100%;
    max-width: 100vw;
}

.container {
    width: 100%;
    max-width: min(1400px, calc(100vw - 40px));
    margin: 0 auto;
    padding: 0 20px;
}

header {
    padding: 1rem 0;
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 100;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transition: all var(--transition-time);
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

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

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--neutral-dark);
    text-decoration: none;
    letter-spacing: -0.5px;
    line-height: 1.1;
    transition: all 0.3s ease;
}

.logo-subtitle {
    font-size: 0.85rem;
    color: #666;
    font-weight: 400;
    margin-top: 2px;
    letter-spacing: 0.3px;
}

.logo:hover {
    transform: translateY(-1px);
}

.navigation ul {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.navigation a {
    text-decoration: none;
    color: var(--neutral-dark);
    font-weight: 500;
    font-size: 1.1rem;
    transition: all var(--transition-time);
    position: relative;
}

.navigation a:after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    transition: width var(--transition-time);
}

.navigation a.science:after {
    background-color: var(--science-primary);
}

.navigation a:hover:after {
    width: 100%;
}

.hero {
    background: var(--science-gradient);
    color: white;
    padding: 8rem 0 4rem;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100" viewBox="0 0 100 100"><circle cx="10" cy="10" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="50" cy="10" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="90" cy="10" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="10" cy="50" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="50" cy="50" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="90" cy="50" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="10" cy="90" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="50" cy="90" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="90" cy="90" r="2" fill="rgba(255,255,255,0.1)"/></svg>');
    opacity: 0.4;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 1rem;
    letter-spacing: -1px;
}

.hero p {
    font-size: 1.4rem;
    opacity: 0.9;
    max-width: 700px;
}

.topics-grid {
    padding: 3rem 0;
}

.section-heading {
    margin-bottom: 3rem;
}

.section-heading h2 {
    font-size: 2.6rem;
    color: var(--neutral-dark);
    font-weight: 700;
    margin-bottom: 1rem;
}

.section-heading p {
    font-size: 1.2rem;
    color: #666;
    max-width: 800px;
}

.topic-categories {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 2.5rem;
}

.topic-card {
    background: white;
    border-radius: var(--card-border-radius);
    overflow: hidden;
    box-shadow: var(--box-shadow);
    transition: all var(--transition-time);
    position: relative;
}

.topic-card::before {
    content: none;
}

.topic-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 15px 30px rgba(0, 0, 0, 0.15);
}

.evolution.topic-card:hover {
    box-shadow: 0 15px 30px rgba(39, 174, 96, 0.2);
}

.human-evolution.topic-card:hover {
    box-shadow: 0 15px 30px rgba(230, 126, 34, 0.2);
}

.earth.topic-card:hover {
    box-shadow: 0 15px 30px rgba(41, 128, 185, 0.2);
}

.dating.topic-card:hover {
    box-shadow: 0 15px 30px rgba(211, 84, 0, 0.2);
}

.astronomy.topic-card:hover {
    box-shadow: 0 15px 30px rgba(52, 73, 94, 0.2);
}

.biblical-science.topic-card:hover {
    box-shadow: 0 15px 30px rgba(106, 76, 147, 0.2);
}

.topic-card-header {
    padding: 1rem;
    color: white;
    position: relative;
    display: flex;
    align-items: center;
    gap: 1rem;
}

.topic-card-header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url('data:image/svg+xml;utf8,<svg width="100" height="100" viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg"><circle cx="25" cy="25" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="50" cy="25" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="75" cy="25" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="25" cy="50" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="50" cy="50" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="75" cy="50" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="25" cy="75" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="50" cy="75" r="2" fill="rgba(255,255,255,0.1)"/><circle cx="75" cy="75" r="2" fill="rgba(255,255,255,0.1)"/></svg>');
    opacity: 0.3;
}

.biblical-science .topic-card-header {
    background: var(--biblical-perspectives-primary);
}

.evolution .topic-card-header {
    background: var(--evolution-color);
}

.human-evolution .topic-card-header {
    background: var(--human-evolution-color);
}

.earth .topic-card-header {
    background: var(--earth-color);
}

.dating .topic-card-header {
    background: var(--dating-color);
}

.astronomy .topic-card-header {
    background: var(--astronomy-color);
}

.topic-card-icon {
    font-size: 2.5rem;
    margin-bottom: 0;
    position: relative;
    flex-shrink: 0;
}

.topic-card-title {
    font-size: 1.6rem;
    font-weight: 700;
    margin-bottom: 0.2rem;
    position: relative;
}

.topic-card-description {
    font-size: 1rem;
    opacity: 0.9;
    position: relative;
}

.topic-card-content {
    padding: 1rem;
}

.topic-links {
    list-style: none;
}

.topic-links li {
    margin-bottom: 0.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid #e0e0e0;
}

.topic-links li:last-child {
    margin-bottom: 0;
    padding-bottom: 0;
    border-bottom: none;
}

.topic-links a {
    display: flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    color: var(--neutral-dark);
    font-weight: 500;
    padding: 0.4rem 0.6rem;
    border-radius: 8px;
    transition: all var(--transition-time);
}

.biblical-science .topic-links a:hover {
    background: rgba(106, 76, 147, 0.1);
    color: var(--biblical-perspectives-primary);
}

.evolution .topic-links a:hover {
    background: rgba(39, 174, 96, 0.1);
    color: var(--evolution-color);
}

.human-evolution .topic-links a:hover {
    background: rgba(230, 126, 34, 0.1);
    color: var(--human-evolution-color);
}

.earth .topic-links a:hover {
    background: rgba(41, 128, 185, 0.1);
    color: var(--earth-color);
}

.dating .topic-links a:hover {
    background: rgba(211, 84, 0, 0.1);
    color: var(--dating-color);
}

.astronomy .topic-links a:hover {
    background: rgba(52, 73, 94, 0.1);
    color: var(--astronomy-color);
}

.topic-links a i {
    font-size: 1.2rem;
}

footer {
    background-color: var(--neutral-dark);
    color: white;
    padding: 4rem 0 2rem;
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr auto;
    gap: 4rem;
    align-items: start;
}

.footer-logo {
    font-size: 1.8rem;
    font-weight: 700;
    color: white;
    margin-bottom: 1rem;
}

.footer-description {
    max-width: 400px;
    opacity: 0.7;
    margin-bottom: 0;
}

.footer-heading {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: 0.8rem;
}

.footer-links a {
    color: rgba(255, 255, 255, 0.7);
    text-decoration: none;
    transition: color var(--transition-time);
}

.footer-links a:hover {
    color: white;
}

.copyright {
    margin-top: 4rem;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
    color: rgba(255, 255, 255, 0.5);
}

.changelog-button {
    display: inline-block;
    padding: 0.8rem 1.5rem;
    background-color: var(--science-primary);
    color: white;
    text-decoration: none;
    border-radius: 50px; /* Fully rounded */
    font-weight: 500;
    transition: background-color var(--transition-time), transform var(--transition-time);
    box-shadow: var(--box-shadow);
    margin-top: 1.5rem; /* Space below description */
}

.changelog-button:hover {
    background-color: var(--science-accent);
    transform: translateY(-2px);
}

.to-top-button {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: var(--science-primary);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.15);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-time);
    z-index: 99;
}

.to-top-button.visible {
    opacity: 1;
    visibility: visible;
}

.to-top-button:hover {
    background: var(--science-accent);
    transform: translateY(-3px);
    box-shadow: 0 6px 15px rgba(0, 0, 0, 0.2);
}

.mobile-menu-button {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--neutral-dark);
}

/* Animation classes */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.active {
    opacity: 1;
    transform: translateY(0);
}

@media (max-width: 992px) {
    .footer-content {
        grid-template-columns: 1fr;
        gap: 3rem;
    }
}

@media (max-width: 768px) {
    .hero {
        padding: 8rem 0 4rem;
    }

    .hero h1 {
        font-size: 2.6rem;
    }

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

    .topic-categories {
        grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    }

    .section-heading h2 {
        font-size: 2.2rem;
    }
}

@media (max-width: 576px) {
    .header-container {
        padding: 0 15px;
    }

    .mobile-menu-button {
        display: block;
    }

    .navigation {
        position: fixed;
        top: 70px;
        left: 0;
        width: 100%;
        background: white;
        box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
        z-index: 99;
        display: none;
    }
    
    .navigation.active {
        display: block;
    }

    .navigation ul {
        flex-direction: column;
        gap: 0;
        padding: 0;
    }
    
    .navigation ul li {
        width: 100%;
    }
    
    .navigation ul li a {
        display: block;
        padding: 15px 20px;
        border-bottom: 1px solid rgba(0,0,0,0.05);
    }

    .hero h1 {
        font-size: 2.2rem;
    }

    .section-heading h2 {
        font-size: 2.2rem;
    }

    .topic-categories {
        grid-template-columns: 1fr;
    }
}