/* 侧边栏 */
.sidebar {
    width: 260px;
    background: linear-gradient(180deg, #000000 100%, #764ba2 100%);
    color: white;
    display: flex;
    flex-direction: column;
    box-shadow: 2px 0 10px rgba(0,0,0,0.1);
}

.logo {
    padding: 30px 20px;
    border-bottom: 1px solid rgba(255,255,255,0.1);
}

.logo h2 {
    font-size: 1.5rem;
    font-weight: 600;
}

.nav-menu {
    padding: 20px 0;
    flex: 1;
}

.nav-item {
    width: 100%;
    padding: 15px 25px;
    background: none;
    border: none;
    color: rgba(255,255,255,0.8);
    text-align: left;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 15px;
    transition: all 0.3s;
}

.nav-item:hover {
    background: rgba(255,255,255,0.1);
    color: white;
}

.nav-item.active {
    background: rgba(255,255,255,0.15);
    color: white;
    border-left: 4px solid white;
}

.nav-item .icon {
    font-size: 20px;
}

/* 主内容区 */
.main-content {
    flex: 1;
    overflow: hidden;
    position: relative;
}

.page {
    display: none;
    height: 100%;
    flex-direction: column;
}

.page.active {
    display: flex;
}

/* 页面头部 */
.page-header,
.chat-header {
    padding: 25px 30px;
    background: white;
    border-bottom: 1px solid #e5e7eb;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.page-header h1,
.chat-header h1 {
    font-size: 1.8rem;
    color: #1f2937;
    font-weight: 600;
}