/* 通用重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body {
    font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: #f0f2f5;
    height: 100vh;
}

/* ========== 登录页样式（保留原样） ========== */
.login-body {
    background: linear-gradient(135deg, #0f2027 0%, #203a43 50%, #2c5364 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    overflow: hidden;
}
.login-container {
    width: 420px;
    padding: 40px;
    background: rgba(255, 255, 255, 0.08);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: 24px;
    box-shadow: 0 25px 50px rgba(0,0,0,0.3);
    border: 1px solid rgba(255,255,255,0.15);
    color: #fff;
    text-align: center;
}
.login-container h1 {
    font-size: 32px;
    margin-bottom: 8px;
    font-weight: 300;
    letter-spacing: 2px;
}
.login-container .subtitle {
    font-size: 14px;
    margin-bottom: 35px;
    color: rgba(255,255,255,0.6);
}
.input-group {
    margin-bottom: 24px;
    text-align: left;
}
.input-group label {
    display: block;
    margin-bottom: 6px;
    font-size: 13px;
    color: rgba(255,255,255,0.7);
    text-transform: uppercase;
    letter-spacing: 1px;
}
.input-group input {
    width: 100%;
    padding: 14px 16px;
    background: rgba(255,255,255,0.1);
    border: 1px solid rgba(255,255,255,0.2);
    border-radius: 12px;
    color: #fff;
    font-size: 15px;
    outline: none;
    transition: 0.3s;
}
.input-group input:focus {
    border-color: #4facfe;
    background: rgba(255,255,255,0.15);
}
.btn-login {
    width: 100%;
    padding: 14px;
    background: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    border: none;
    border-radius: 12px;
    color: #fff;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: 0.3s;
    letter-spacing: 2px;
    margin-top: 10px;
}
.btn-login:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 25px rgba(79,172,254,0.4);
}
.error-msg {
    background: rgba(255,80,80,0.2);
    border: 1px solid rgba(255,80,80,0.5);
    color: #ffb3b3;
    padding: 10px;
    border-radius: 8px;
    margin-bottom: 20px;
    font-size: 14px;
}

/* ========== 主布局 ========== */
.app-container {
    display: flex;
    height: 100vh;
}

/* 侧边栏整体 */
.sidebar {
    width: 260px;
    background: #0b1a2f;            /* 深蓝黑色底色，清晰不暗 */
    color: #fff;
    display: flex;
    flex-direction: column;
    box-shadow: 2px 0 12px rgba(0,0,0,0.3);
    z-index: 10;
}
.sidebar-logo {
    padding: 28px 24px;
    border-bottom: 1px solid rgba(255,255,255,0.12);
    background: #091525;
}
.sidebar-logo h2 {
    font-size: 22px;
    font-weight: 500;
    letter-spacing: 2px;
    color: #ffffff;
    text-shadow: 0 2px 4px rgba(0,0,0,0.3);
}

/* 菜单容器 */
.sidebar-menu {
    list-style: none;
    padding: 12px 0;
    flex: 1;
    overflow-y: auto;
}
.sidebar-menu .menu-group {
    margin-bottom: 2px;
}

/* 菜单组标题（可点击折叠） */
.menu-title {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 24px 10px;
    color: #b0c6df;                /* 浅蓝灰，清晰不刺眼 */
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    font-weight: 600;
    cursor: pointer;
    user-select: none;
    transition: color 0.2s;
}
.menu-title:hover {
    color: #ffffff;
}
/* 箭头 */
.arrow {
    display: inline-block;
    width: 0;
    height: 0;
    border-left: 4px solid transparent;
    border-right: 4px solid transparent;
    border-top: 5px solid #b0c6df;
    transition: transform 0.3s;
}
.menu-group.open .arrow {
    transform: rotate(180deg);
    border-top-color: #ffffff;
}

/* 子菜单默认隐藏 */
.sub-menu {
    list-style: none;
    padding: 0;
    display: none;
}
/* 展开后显示 */
.menu-group.open .sub-menu {
    display: block;
}

/* 子菜单链接（有子菜单的情况） */
.sub-menu li a {
    display: flex;
    align-items: center;
    padding: 11px 24px 11px 42px;  /* 缩进体现层级 */
    color: #c0d0e5;
    text-decoration: none;
    font-size: 14px;
    transition: all 0.2s;
    border-left: 3px solid transparent;
    background: transparent;
}
.sub-menu li a:hover {
    background: rgba(255,255,255,0.08);
    color: #ffffff;
}
.sub-menu li a.active {
    background: rgba(33, 150, 243, 0.15);   /* 蓝色半透明背景 */
    color: #4da3ff;
    border-left: 3px solid #4da3ff;
    font-weight: 500;
}

/* 单页面菜单（没有子菜单的独立链接） */
.single {
    display: flex;
    align-items: center;
    padding: 12px 24px;
    color: #c0d0e5;
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.2s;
    border-left: 3px solid transparent;
}
.single:hover {
    background: rgba(255,255,255,0.08);
    color: #ffffff;
}
.single.active {
    background: rgba(33, 150, 243, 0.15);
    color: #4da3ff;
    border-left-color: #4da3ff;
}

/* 图标统一 */
.sidebar-menu .icon {
    margin-right: 10px;
    font-size: 16px;
    width: 20px;
    text-align: center;
    opacity: 0.9;
}

/* 滚动条 */
.sidebar-menu::-webkit-scrollbar { width: 4px; }
.sidebar-menu::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.25); border-radius: 2px; }
.sidebar-menu::-webkit-scrollbar-track { background: transparent; }

/* ========== 主内容区域（完全保留） ========== */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow-y: auto;
}
.top-bar {
    height: 64px;
    background: #fff;
    display: flex;
    align-items: center;
    justify-content: flex-end;
    padding: 0 32px;
    box-shadow: 0 1px 4px rgba(0,0,0,0.05);
    gap: 20px;
}
.user-info {
    color: #333;
    font-size: 14px;
}
.logout-btn {
    color: #ff4d4f;
    text-decoration: none;
    font-size: 14px;
    padding: 6px 16px;
    border: 1px solid #ff4d4f;
    border-radius: 6px;
    transition: 0.2s;
}
.logout-btn:hover {
    background: #ff4d4f;
    color: #fff;
}
.content-area {
    padding: 32px;
    flex: 1;
}
.page-card {
    background: #fff;
    border-radius: 16px;
    padding: 48px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.04);
    text-align: center;
    min-height: 400px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
.page-card h1 {
    font-size: 28px;
    font-weight: 400;
    color: #001529;
    margin-bottom: 16px;
}
.placeholder-text {
    color: #999;
    font-size: 16px;
}