/* 底部导航栏公共样式 */
:root {
    --bottom-nav-height: 56px;
}
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 100%;
    max-width: 750px;
    background: rgba(255,255,255,0.92);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    display: flex;
    align-items: flex-end;
    justify-content: space-around;
    padding: 4px 0;
    padding-bottom: calc(4px + env(safe-area-inset-bottom));
    border-top: 1px solid rgba(0,0,0,0.04);
    z-index: 100;
}
.bottom-nav .nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    cursor: pointer;
    padding: 4px 12px;
    transition: color 0.25s, transform 0.25s cubic-bezier(0.34, 1.56, 0.64, 1);
    color: #999;
    font-size: 10px;
    position: relative;
}
.bottom-nav .nav-item .nav-icon {
    font-size: 22px;
    margin-bottom: 2px;
    transition: transform 0.25s cubic-bezier(0.34, 1.56, 0.64, 1);
}
.bottom-nav .nav-item:active {
    transform: scale(0.9);
}
.bottom-nav .nav-item.active {
    color: #409eff;
}
.bottom-nav .nav-item.active .nav-icon {
    transform: scale(1.15);
}
/* 激活态底部指示条 */
.bottom-nav .nav-item.active::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 50%;
    transform: translateX(-50%);
    width: 16px;
    height: 3px;
    border-radius: 2px;
    background: #409eff;
    animation: navIndicatorIn 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}
@keyframes navIndicatorIn {
    from { width: 0; opacity: 0; }
    to { width: 16px; opacity: 1; }
}
.bottom-nav .nav-item-center {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 0 12px;
    margin-top: -24px;
}
.bottom-nav .nav-item-center .center-logo {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: linear-gradient(135deg, #409eff, #337ecc);
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 16px;
    font-weight: 700;
    border: 3px solid #fff;
    box-shadow: 0 4px 12px rgba(64,158,255,0.4);
    transition: transform 0.25s cubic-bezier(0.34, 1.56, 0.64, 1), box-shadow 0.25s;
}
/* 中间LOGO图片样式（替代原QT文字圆形） */
.bottom-nav .nav-item-center .center-logo-img {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid #fff;
    box-shadow: 0 4px 12px rgba(64,158,255,0.4);
    transition: transform 0.25s cubic-bezier(0.34, 1.56, 0.64, 1), box-shadow 0.25s;
}
.bottom-nav .nav-item-center:active .center-logo-img {
    transform: scale(0.9);
    box-shadow: 0 2px 6px rgba(64,158,255,0.3);
}
.bottom-nav .nav-item-center:active .center-logo {
    transform: scale(0.9);
    box-shadow: 0 2px 6px rgba(64,158,255,0.3);
}
.bottom-nav .nav-item-center .center-text {
    font-size: 10px;
    color: #999;
    margin-top: 3px;
}