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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    background: white;
    padding: 20px;
    margin-bottom: 30px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

header h1 {
    color: #2c3e50;
    font-size: 28px;
}

.user-info {
    font-size: 14px;
}

.user-info a {
    margin-left: 15px;
    color: #e74c3c;
    text-decoration: none;
}

nav {
    margin-bottom: 20px;
}

nav a {
    color: #3498db;
    text-decoration: none;
    font-size: 14px;
}

nav a:hover {
    text-decoration: underline;
}

main {
    background: white;
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

h2 {
    color: #2c3e50;
    margin-bottom: 20px;
    font-size: 24px;
}

.login-form, .register-form {
    max-width: 400px;
    margin: 50px auto;
    padding: 30px;
    background: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
    color: #555;
}

.form-group input {
    width: 100%;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 14px;
}

.form-group input:focus {
    outline: none;
    border-color: #3498db;
}

button {
    background: #3498db;
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
}

button:hover {
    background: #2980b9;
}

button[type="button"] {
    background: #95a5a6;
    margin-left: 10px;
}

button[type="button"]:hover {
    background: #7f8c8d;
}

.category-card, .topic-card, .post-card {
    background: #f8f9fa;
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 6px;
    border-left: 4px solid #3498db;
}

.category-card h3, .topic-card h3 {
    color: #2c3e50;
    margin-bottom: 10px;
}

.category-card p {
    color: #666;
    margin-bottom: 15px;
}

.category-card a, .topic-card a {
    color: #3498db;
    text-decoration: none;
    font-weight: 500;
}

.category-card a:hover, .topic-card a:hover {
    text-decoration: underline;
}

.topic-meta {
    font-size: 14px;
    color: #666;
    margin-top: 10px;
}

.post-card {
    border-left-color: #2ecc71;
}

.post-author {
    font-weight: 600;
    color: #2c3e50;
    margin-bottom: 10px;
}

.post-content {
    color: #555;
    line-height: 1.8;
    white-space: pre-wrap;
}

.reply-form {
    margin-top: 30px;
    padding-top: 30px;
    border-top: 2px solid #ecf0f1;
}

.reply-form h3 {
    margin-bottom: 15px;
    color: #2c3e50;
}

textarea {
    width: 100%;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-family: inherit;
    font-size: 14px;
    resize: vertical;
}

textarea:focus {
    outline: none;
    border-color: #3498db;
}