:root {
    --primary-color: #2c3e50;
    --secondary-color: #7f8c8d;
    --accent-color: #3498db;
    --bg-color: #f8f9fa;
    --text-color: #333;
    --border-color: #e9ecef;
    --container-width: 800px;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

a {
    color: var(--accent-color);
    text-decoration: none;
    transition: color 0.2s ease;
}

a:hover {
    color: #2980b9;
    text-decoration: underline;
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
header {
    background-color: #fff;
    border-bottom: 1px solid var(--border-color);
    padding: 20px 0;
    margin-bottom: 40px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.02);
}

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

header h1 a {
    color: var(--primary-color);
    text-decoration: none;
    font-size: 1.5rem;
    font-weight: 700;
}

header h1 a:hover {
    text-decoration: none;
}

nav a {
    color: var(--secondary-color);
    margin-left: 20px;
    text-decoration: none;
    font-weight: 500;
}

nav a.active, nav a:hover {
    color: var(--accent-color);
}

/* Main Content */
main {
    flex: 1;
}

/* Post List */
.post-item {
    background: #fff;
    padding: 24px;
    border-radius: 8px;
    margin-bottom: 24px;
    border: 1px solid var(--border-color);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.post-item:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}

.post-title {
    font-size: 1.4rem;
    margin-bottom: 8px;
}

.post-title a {
    color: var(--primary-color);
}

.post-title a:hover {
    color: var(--accent-color);
    text-decoration: none;
}

.post-meta {
    font-size: 0.9rem;
    color: var(--secondary-color);
    margin-bottom: 12px;
    display: flex;
    align-items: center;
    gap: 12px;
}

.post-category {
    background-color: #f1f3f5;
    color: #495057;
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 0.8rem;
    font-weight: 500;
}

.post-excerpt {
    color: #555;
}

/* Filters */
.filter-section {
    margin-bottom: 24px;
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.filter-btn {
    background: #fff;
    border: 1px solid var(--border-color);
    padding: 6px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9rem;
    color: var(--secondary-color);
    transition: all 0.2s ease;
    outline: none;
}

.filter-btn:hover {
    border-color: var(--accent-color);
    color: var(--accent-color);
}

.filter-btn.active {
    background: var(--accent-color);
    color: #fff;
    border-color: var(--accent-color);
}

/* Post Content */
.post-content {
    background: #fff;
    padding: 40px;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    margin-bottom: 40px;
}

.post-content h1, .post-content h2, .post-content h3 {
    margin-top: 1.5em;
    margin-bottom: 0.5em;
    color: var(--primary-color);
}

.post-content p {
    margin-bottom: 1.2em;
}

.post-content ul, .post-content ol {
    margin-bottom: 1.2em;
    padding-left: 20px;
}

.post-content li {
    margin-bottom: 0.5em;
}

.post-header {
    text-align: center;
    margin-bottom: 40px;
    padding-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
}

.post-header h1 {
    margin-top: 0;
    font-size: 2rem;
}

.post-header .post-meta {
    justify-content: center;
}

/* Footer */
footer {
    text-align: center;
    padding: 30px 0;
    color: var(--secondary-color);
    font-size: 0.9rem;
    margin-top: 40px;
    border-top: 1px solid var(--border-color);
    background-color: #fff;
}