:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    /* 浅色主题变量 */
    --bg-dark: #f8fafc;
    /* 整体背景：浅灰白 */
    --bg-card: #ffffff;
    /* 卡片背景：纯白 */
    --bg-hover: #f1f5f9;
    /* 悬停背景：极浅灰 */
    --text-primary: #0f172a;
    /* 主文字：深蓝黑 */
    --text-secondary: #475569;
    /* 次要文字：深灰 */
    --text-muted: #94a3b8;
    /* 弱化文字：中灰 */
    --border: #e2e8f0;
    /* 边框：浅灰 */
    --success: #22c55e;
    --warning: #f59e0b;
    --error: #ef4444;
    --radius: 12px;
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-dark);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
}

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

.center-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    padding: 20px;
}

/* ========== 卡片 ========== */
.card {
    background: var(--bg-card);
    border-radius: var(--radius);
    padding: 32px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border);
}

.card-header {
    margin-bottom: 24px;
    text-align: center;
}

.card-header h1 {
    font-size: 28px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-light), var(--primary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.card-header p {
    color: var(--text-secondary);
    margin-top: 8px;
}

/* ========== 表单 ========== */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    color: var(--text-secondary);
}

.form-control {
    width: 100%;
    padding: 14px 16px;
    font-size: 16px;
    color: var(--text-primary);
    background: var(--bg-dark);
    border: 1px solid var(--border);
    border-radius: 8px;
    transition: all 0.2s;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

.form-control::placeholder {
    color: var(--text-muted);
}

/* ========== 按钮 ========== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 14px 24px;
    font-size: 16px;
    font-weight: 600;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: white;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.4);
}

.btn-secondary {
    background: var(--bg-hover);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--border);
}

.btn-danger {
    background: var(--error);
    color: white;
}

.btn-block {
    width: 100%;
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

/* ========== 导航栏 ========== */
.navbar {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    padding: 16px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 100;
}

.navbar-brand {
    font-size: 20px;
    font-weight: 700;
    color: var(--primary-light);
    text-decoration: none;
}

.navbar-user {
    display: flex;
    align-items: center;
    gap: 16px;
}

.navbar-email {
    color: var(--text-secondary);
    font-size: 14px;
}

/* ========== 邮件列表 ========== */
.email-list {
    margin-top: 20px;
}

.email-item {
    display: flex;
    align-items: flex-start;
    gap: 16px;
    padding: 16px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 12px;
    cursor: pointer;
    transition: all 0.2s;
}

.email-item:hover {
    background: var(--bg-hover);
    transform: translateX(4px);
}

.email-item.unread {
    border-left: 3px solid var(--primary);
}

.email-item.unread .email-subject {
    font-weight: 600;
}

.email-avatar {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 600;
    font-size: 18px;
    flex-shrink: 0;
}

.email-content {
    flex: 1;
    min-width: 0;
}

.email-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 4px;
}

.email-from {
    font-weight: 500;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.email-time {
    color: var(--text-muted);
    font-size: 13px;
    flex-shrink: 0;
}

.email-subject {
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.email-preview {
    color: var(--text-muted);
    font-size: 14px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    margin-top: 4px;
}

/* ========== 邮件详情 ========== */
.email-detail {
    background: var(--bg-card);
    border-radius: var(--radius);
    border: 1px solid var(--border);
    overflow: hidden;
}

.email-detail-header {
    padding: 24px;
    border-bottom: 1px solid var(--border);
}

.email-detail-subject {
    font-size: 22px;
    font-weight: 600;
    margin-bottom: 16px;
}

.email-detail-meta {
    display: flex;
    gap: 24px;
    color: var(--text-secondary);
    font-size: 14px;
}

.email-detail-body {
    padding: 24px;
    min-height: 300px;
}

/* ========== 管理后台 ========== */
.admin-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
    margin-bottom: 32px;
}

.stat-card {
    background: var(--bg-card);
    border-radius: var(--radius);
    padding: 24px;
    border: 1px solid var(--border);
}

.stat-card h3 {
    color: var(--text-muted);
    font-size: 14px;
    font-weight: 500;
    margin-bottom: 8px;
}

.stat-card .value {
    font-size: 36px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-light), var(--primary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.action-bar {
    display: flex;
    gap: 12px;
    flex-wrap: wrap;
    margin-bottom: 24px;
}

.action-bar .form-control {
    width: auto;
    min-width: 100px;
}

/* ========== 表格 ========== */
.table-container {
    overflow-x: auto;
    background: var(--bg-card);
    border-radius: var(--radius);
    border: 1px solid var(--border);
}

table {
    width: 100%;
    border-collapse: collapse;
}

th,
td {
    padding: 14px 16px;
    text-align: left;
    border-bottom: 1px solid var(--border);
}

th {
    background: var(--bg-hover);
    font-weight: 600;
    color: var(--text-secondary);
    font-size: 13px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

tr:hover td {
    background: var(--bg-hover);
}

/* ========== 模态框 ========== */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.7);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: all 0.2s;
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background: var(--bg-card);
    border-radius: var(--radius);
    max-width: 600px;
    width: 90%;
    max-height: 90vh;
    overflow: auto;
    transform: translateY(-20px);
    transition: transform 0.2s;
}

.modal-overlay.active .modal {
    transform: translateY(0);
}

.modal-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h2 {
    font-size: 20px;
}

.modal-close {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 24px;
    cursor: pointer;
    padding: 4px;
}

.modal-close:hover {
    color: var(--text-primary);
}

.modal-body {
    padding: 24px;
}

.modal-footer {
    padding: 16px 24px;
    border-top: 1px solid var(--border);
    display: flex;
    justify-content: flex-end;
    gap: 12px;
}

/* ========== 消息提示 ========== */
.toast {
    position: fixed;
    bottom: 24px;
    right: 24px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 16px 20px;
    box-shadow: var(--shadow);
    transform: translateY(100px);
    opacity: 0;
    transition: all 0.3s;
    z-index: 1001;
}

.toast.show {
    transform: translateY(0);
    opacity: 1;
}

.toast.success {
    border-left: 3px solid var(--success);
}

.toast.error {
    border-left: 3px solid var(--error);
}

/* ========== 分页 ========== */
.pagination {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-top: 24px;
}

.pagination button {
    padding: 10px 16px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.2s;
}

.pagination button:hover:not(:disabled) {
    background: var(--bg-hover);
}

.pagination button.active {
    background: var(--primary);
    border-color: var(--primary);
}

.pagination button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* ========== 加载状态 ========== */
.loading {
    display: flex;
    justify-content: center;
    padding: 40px;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* ========== 空状态 ========== */
.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-muted);
}

.empty-state svg {
    width: 80px;
    height: 80px;
    margin-bottom: 16px;
    opacity: 0.5;
}

.empty-state h3 {
    font-size: 18px;
    margin-bottom: 8px;
    color: var(--text-secondary);
}

/* ========== 响应式 ========== */
@media (max-width: 768px) {
    .card {
        padding: 24px;
    }

    .navbar {
        flex-direction: column;
        gap: 12px;
    }

    .action-bar {
        flex-direction: column;
    }

    .action-bar .form-control,
    .action-bar .btn {
        width: 100%;
    }

    .email-detail-meta {
        flex-direction: column;
        gap: 8px;
    }
}

/* ========== 登录页 ========== */
.login-card {
    width: 100%;
    max-width: 420px;
}

.login-logo {
    font-size: 48px;
    margin-bottom: 8px;
}

.login-tabs {
    display: flex;
    margin-bottom: 24px;
    border-bottom: 1px solid var(--border);
}

.login-tab {
    flex: 1;
    padding: 12px;
    text-align: center;
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s;
    border-bottom: 2px solid transparent;
    margin-bottom: -1px;
}

.login-tab:hover {
    color: var(--text-secondary);
}

.login-tab.active {
    color: var(--primary-light);
    border-bottom-color: var(--primary);
}