.header {
    position: sticky; top: 0; z-index: 1000;
    height: var(--header-height);
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
}
.header__container {
    max-width: 1200px; margin: 0 auto; height: 100%;
    display: flex; align-items: center; justify-content: space-between;
    padding: 0 24px;
}
.header__logo { font-size: 20px; font-weight: 700; color: var(--color-primary); }
.nav__list { display: flex; gap: 32px; }
.nav__link {
    font-size: 15px; padding: 20px 0; display: block;
    transition: var(--transition);
}
.nav__link:hover { color: var(--color-primary); }

/* 子菜单 */
.nav__item--has-submenu { position: relative; }
.nav__submenu {
    position: absolute; top: 100%; left: 50%; transform: translateX(-50%);
    min-width: 140px; background: var(--color-bg);
    border: 1px solid var(--color-border); border-radius: var(--radius);
    box-shadow: var(--shadow-card-hover);
    opacity: 0; visibility: hidden; transform: translateX(-50%) translateY(8px);
    transition: var(--transition);
}
.nav__submenu a {
    display: block; padding: 10px 20px; font-size: 14px; white-space: nowrap;
    transition: var(--transition);
}
.nav__submenu a:hover { background: var(--color-bg-gray); color: var(--color-primary); }
.nav__item--has-submenu:hover .nav__submenu {
    opacity: 1; visibility: visible; transform: translateX(-50%) translateY(0);
}