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

/* 隐藏类 */
.hidden {
    display: none !important;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background-color: #f5f5f5;
    color: #333;
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* 导航栏 */
.navbar {
    background-color: white;
    padding: 8px 20px;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.08);
    position: sticky;
    top: 0;
    z-index: 1000;
}

.navbar-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
}

.navbar-brand {
    font-size: 16px;
    font-weight: 700;
    color: #333;
    text-decoration: none;
}

.navbar-nav {
    display: flex;
    list-style: none;
    gap: 16px;
}

.nav-link {
    color: #666;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s ease;
    position: relative;
    font-size: 14px;
    padding: 4px 0;
}

.nav-link:hover {
    color: #333;
}

.nav-link.active {
    color: #333;
    font-weight: 600;
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 2px;
    background-color: #333;
    border-radius: 1px;
}

.container {
    max-width: 800px;
    width: 90%;
    margin: 0 auto;
    text-align: center;
    padding: 40px 20px;
}

.header {
    margin-bottom: 60px;
}

.logo {
    font-size: 48px;
    font-weight: 700;
    color: #333;
    margin-bottom: 20px;
    letter-spacing: -1px;
}

.subtitle {
    font-size: 18px;
    color: #666;
    line-height: 1.8;
    max-width: 600px;
    margin: 0 auto;
}

.main {
    margin-bottom: 60px;
}

.btn-group {
    display: flex;
    gap: 30px;
    justify-content: center;
    margin-bottom: 60px;
    flex-wrap: wrap;
}

.btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-decoration: none;
    padding: 30px 40px;
    border-radius: 8px;
    transition: all 0.3s ease;
    min-width: 250px;
}

.primary-btn {
    background-color: #333;
    color: white;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.secondary-btn {
    background-color: white;
    color: #333;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    border: 1px solid #e0e0e0;
}

.btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
}

.btn-icon {
    font-size: 48px;
    margin-bottom: 20px;
}

.btn-text {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 10px;
}

.btn-desc {
    font-size: 14px;
    opacity: 0.8;
}

.stats {
    display: flex;
    justify-content: center;
    gap: 60px;
    flex-wrap: wrap;
}

.stat-item {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 36px;
    font-weight: 700;
    color: #333;
    margin-bottom: 10px;
}

.stat-label {
    font-size: 14px;
    color: #666;
}

.footer {
    margin-top: 60px;
    padding-top: 20px;
    border-top: 1px solid #e0e0e0;
}

.footer p {
    font-size: 14px;
    color: #999;
}

/* 表单页面样式 */
.form-container {
    max-width: 600px;
    margin: 0 auto;
    background-color: white;
    border-radius: 8px;
    padding: 40px;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
}

.form-group {
    margin-bottom: 24px;
    text-align: left;
}

.form-group label {
    display: block;
    font-size: 14px;
    font-weight: 600;
    color: #333;
    margin-bottom: 8px;
}

.form-group label .limit {
    font-weight: 400;
    font-size: 12px;
    color: #666;
    margin-left: 8px;
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 16px;
    border: 2px solid #e0e0e0;
    border-radius: 6px;
    font-size: 16px;
    transition: all 0.3s ease;
    font-family: inherit;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: #333;
    box-shadow: 0 0 0 4px rgba(0, 0, 0, 0.1);
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

.contact-options {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 12px;
}

.captcha-container {
    display: flex;
    align-items: center;
    gap: 12px;
}

.captcha-image {
    width: 120px;
    height: 48px;
    background-color: #f5f5f5;
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 18px;
    letter-spacing: 2px;
    cursor: pointer;
    user-select: none;
    border: 1px solid #e0e0e0;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.submit-btn {
    width: 100%;
    padding: 16px;
    background-color: #333;
    color: white;
    border: none;
    border-radius: 6px;
    font-size: 18px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 30px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.submit-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
}

/* 信件列表页面 */
.letters-container {
    max-width: 800px;
    margin: 0 auto;
}

.letter-item {
    background-color: white;
    border-radius: 8px;
    padding: 30px;
    margin-bottom: 20px;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
    transition: all 0.3s ease;
}

.letter-item:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.15);
}

.letter-item h3 {
    font-size: 20px;
    font-weight: 600;
    color: #333;
    margin-bottom: 15px;
}

.letter-meta {
    font-size: 14px;
    color: #666;
    margin-bottom: 15px;
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
}

.letter-content {
    font-size: 16px;
    line-height: 1.6;
    color: #333;
    margin-bottom: 20px;
    padding: 20px;
    background-color: #f5f5f5;
    border-radius: 6px;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.05);
}

.letter-actions {
    display: flex;
    gap: 10px;
}

.action-btn {
    padding: 8px 16px;
    border: none;
    border-radius: 4px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
}

.action-btn.primary {
    background-color: #333;
    color: white;
}

.action-btn.secondary {
    background-color: #f5f5f5;
    color: #333;
    border: 1px solid #e0e0e0;
}

.action-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
}

.empty-state p {
    font-size: 18px;
    color: #666;
    margin-bottom: 20px;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .navbar .container {
        flex-direction: column;
        gap: 12px;
        text-align: center;
    }
    
    .navbar-nav {
        gap: 16px;
    }
    
    .logo {
        font-size: 36px;
    }
    
    .subtitle {
        font-size: 16px;
    }
    
    .btn-group {
        flex-direction: column;
        align-items: center;
    }
    
    .btn {
        width: 100%;
        max-width: 300px;
    }
    
    .stats {
        gap: 40px;
    }
    
    .contact-options {
        grid-template-columns: 1fr;
    }
    
    .captcha-container {
        flex-direction: column;
        align-items: stretch;
    }
    
    .captcha-image {
        width: 100%;
        height: 56px;
    }
    
    .form-container {
        padding: 30px 20px;
    }
    
    .letter-meta {
        flex-direction: column;
        gap: 10px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 20px 15px;
    }
    
    .logo {
        font-size: 28px;
    }
    
    .btn {
        padding: 20px 30px;
        min-width: 200px;
    }
    
    .btn-icon {
        font-size: 36px;
    }
    
    .btn-text {
        font-size: 18px;
    }
    
    .stat-number {
        font-size: 28px;
    }
    
    .form-group input,
    .form-group textarea,
    .form-group select {
        padding: 12px;
    }
}