:root {
    --background-color: #121212;
    --text-color: #FFFFFF;
    --text-muted: #B0B0B0;
    --header-background: #1A1A1A;
    --header-text-color: #FFFFFF;
    --nav-link-color: #E0E0E0;
    --nav-link-hover-color: #B0B0B0;
    --welcome-section-bg: #1C1C1C;
    --card-bg: #1A1A1A;
    --card-hover-bg: #222222;
    --topic-card-text-color: #FFFFFF;
    --btn-bg: #E0E0E0;
    --btn-hover-bg: #B0B0B0;
    --info-item-bg: #1A1A1A;
    --footer-bg: #1C1C1C;
    --footer-text: #B0B0B0;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    padding: 20px;
}

header {
    background-color: var(--header-background);
    padding: 40px;
    text-align: center;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

header h1 {
    font-size: 3rem;
    color: var(--header-text-color);
    letter-spacing: 2px;
}

nav {
    margin-top: 15px;
}

nav a {
    color: var(--nav-link-color);
    text-decoration: none;
    margin: 0 25px;
    font-size: 1.2rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    transition: color 0.3s ease;
}

nav a:hover {
    color: var(--nav-link-hover-color);
}

.main-container {
    max-width: 1200px;
    margin: 0 auto;
}

.section-title {
    font-size: 2.5rem;
    color: var(--section-title-color);
    margin-bottom: 30px;
    text-align: center;
}

.related-topics {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
    justify-content: space-between;
}

.topic-card {
    background-color: var(--topic-card-background);
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
    width: 30%;
    overflow: hidden;
    transition: transform 0.3s ease;
}

.topic-card img {
    width: 100%;
    height: auto;
    border-bottom: 2px solid var(--topic-card-border-color);
    border-radius: 10px 10px 0 0;
}

.topic-card:hover {
    transform: scale(1.05);
}

.topic-card h3 {
    font-size: 1.8rem;
    color: var(--topic-card-text-color);
    padding: 20px;
    margin-top: 10px;
}

.topic-card p {
    font-size: 1rem;
    color: var(--topic-card-description-color);
    padding: 0 20px 20px;
}

footer {
    background-color: var(--footer-bg);
    padding: 30px;
    text-align: center;
    margin-top: 60px;
    box-shadow: 0 -4px 15px rgba(0, 0, 0, 0.2);
}

footer p {
    color: var(--footer-text);
    font-size: 1rem;
}

@media (max-width: 768px) {
    .topic-card {
        width: 48%;
    }
    .section-title {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .topic-card {
        width: 100%;
    }
}