:root {
    --bg-color: #ffffff;
    --text-color: #333;
    --header-bg: #2c3e50;
    --accent-color: #40B7E5;
    --card-bg: #f8f9fa;
    --meta-color: #666;
    --tag-bg: var(--header-bg);
    --tag-active: var(--header-bg);
    --link-color: var(--accent-color);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background: var(--bg-color);
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem;
}

header {
    margin: -2rem -2rem 4rem -2rem;
    padding: 4rem 2rem;
    text-align: center;
    background: var(--header-bg);
    color: white;
}

h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    font-weight: normal;
}

.section-title {
    font-size: 1.5rem;
    margin: 3rem 0 1.5rem 0;
    color: var(--accent-color);
}

#about {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 4px;
    margin-bottom: 3rem;
    color: var(--text-color);
}

section {
    margin-bottom: 4rem;
}

.post-grid {
    display: grid;
    gap: 2rem;
}

.post-card {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 4px;
    transition: all 0.2s ease;
    color: var(--text-color);
    display: block;
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.post-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}

.post-card::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.05);
    opacity: 0;
    transition: opacity 0.2s ease;
}

.post-card:hover::after {
    opacity: 1;
}

.post-card h3 {
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

.post-meta {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
    font-size: 0.9rem;
    color: var(--meta-color);
}

.tag {
    color: var(--accent-color);
}

.post-links {
    display: none;
}

.topics-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.topic-tag {
    background: transparent;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    font-size: 0.9rem;
    color: var(--header-bg);
    border: 1px solid var(--header-bg);
    cursor: pointer;
    transition: all 0.2s ease;
    outline: none;
}

.topic-tag:hover {
    background: var(--header-bg);
    color: white;
}

.topic-tag.active {
    background: var(--header-bg);
    color: white;
}

.post-card.hidden {
    display: none;
}

footer {
    margin-top: 4rem;
    padding-top: 2rem;
    border-top: 1px solid var(--card-bg);
    text-align: center;
}

.links {
    display: flex;
    justify-content: center;
    gap: 2rem;
}

.links a {
    color: var(--text-color);
    text-decoration: none;
}

.links a:hover {
    color: var(--accent-color);
}

@media (min-width: 640px) {
    .post-grid {
        grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    }
}