:root {
    --modern-bg: #f3f4f6; /* Lighter gray background for page */
    --modern-card-bg: #ffffff;
    --modern-border: #e5e7eb;
    --modern-text-primary: #1f2937;
    --modern-text-secondary: #6b7280;
    --modern-accent: #2563eb; /* Robot Planet Blue */
    --modern-accent-hover: #1d4ed8;
    --modern-radius: 8px; /* Slightly sharper corners for professional look */
    --modern-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --modern-hover-bg: #f3f4f6;
}

/* Layout Overrides */
.parts-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 20px;
    display: flex;
    gap: 20px;
    background-color: var(--modern-bg);
    min-height: calc(100vh - 64px);
    font-family: 'PingFang SC', 'Microsoft YaHei', 'Helvetica Neue', Arial, sans-serif;
}

/* Sidebar Container */
.parts-sidebar {
    width: 260px;
    flex-shrink: 0;
    background: var(--modern-card-bg);
    border-radius: var(--modern-radius);
    box-shadow: 0 2px 8px rgba(0,0,0,0.04);
    overflow: hidden; /* Contains children */
    height: fit-content;
}

/* Sidebar Header ("全部分类") */
.sidebar-header-modern {
    font-size: 16px;
    font-weight: 700;
    color: var(--modern-text-primary);
    padding: 16px 20px;
    background-color: #fff;
    border-bottom: 1px solid var(--modern-border);
    display: flex;
    align-items: center;
}

.sidebar-header-modern::before {
    content: '';
    display: block;
    width: 4px;
    height: 16px;
    background-color: var(--modern-accent);
    margin-right: 10px;
    border-radius: 2px;
}

/* Navigation List */
.modern-nav-list {
    list-style: none;
    padding: 8px 0;
    margin: 0;
}

.modern-nav-item {
    margin-bottom: 2px;
}

/* Category Header (Clickable Parent) */
.modern-nav-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 20px;
    cursor: pointer;
    color: var(--modern-text-primary);
    font-size: 14px;
    font-weight: 500;
    transition: all 0.2s ease;
    user-select: none;
}

.modern-nav-header:hover {
    background-color: var(--modern-hover-bg);
    color: var(--modern-accent);
}

.modern-nav-item.expanded .modern-nav-header {
    color: var(--modern-accent);
    font-weight: 600;
}

/* Arrow Icon */
.modern-nav-header .arrow {
    font-size: 16px;
    color: #9ca3af;
    transition: transform 0.3s ease;
}

.modern-nav-header:hover .arrow {
    color: var(--modern-accent);
}

.modern-nav-item.expanded .arrow {
    transform: rotate(180deg);
    color: var(--modern-accent);
}

/* Sub Navigation (Children) */
.modern-sub-nav {
    padding: 0;
    margin: 0;
    list-style: none;
    background-color: #f9f9f9; /* Slightly darker inner bg */
    overflow: hidden;
    max-height: 0;
    transition: max-height 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.modern-nav-item.expanded .modern-sub-nav {
    max-height: 500px; /* Enough for content */
    padding-bottom: 8px;
    border-bottom: 1px solid #f0f0f0;
}

/* Sub Item */
.modern-sub-item {
    padding: 10px 20px 10px 34px; /* Indented */
    font-size: 13px;
    color: var(--modern-text-secondary);
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
}

.modern-sub-item:hover {
    color: var(--modern-accent);
    background-color: #f0f0f0;
}

.modern-sub-item.active {
    color: var(--modern-accent);
    font-weight: 600;
    background-color: #fff0f0; /* Very light accent bg */
}

.modern-sub-item.active::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background-color: var(--modern-accent);
}

/* Main Content Area adjustments */
.parts-main {
    flex: 1;
    background: var(--modern-card-bg);
    border-radius: var(--modern-radius);
    padding: 24px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.04);
}

/* Toolbar */
.modern-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--modern-border);
}

.result-count {
    color: var(--modern-text-secondary);
    font-size: 14px;
    margin-left: 12px;
}

/* Filters */
.modern-filters {
    margin-bottom: 24px;
    background: #fff;
}

.filter-group {
    display: flex;
    align-items: flex-start;
    padding: 12px 0;
    border-bottom: 1px dashed var(--modern-border);
}

.filter-group:last-child {
    border-bottom: none;
}

.filter-header {
    width: 80px;
    color: var(--modern-text-secondary);
    font-size: 14px;
    padding-top: 6px;
}

.filter-chips {
    flex: 1;
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.filter-chip {
    padding: 4px 12px;
    font-size: 13px;
    color: var(--modern-text-primary);
    cursor: pointer;
    border-radius: 4px;
    transition: all 0.2s;
}

.filter-chip:hover {
    color: var(--modern-accent);
}

.filter-chip.active {
    background-color: var(--modern-accent);
    color: #fff;
}

/* Grid */
.modern-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 20px;
}

/* Modern Card Style for Products (matching the theme) */
.product-card-modern {
    background: #fff;
    border: 1px solid var(--modern-border);
    border-radius: var(--modern-radius);
    overflow: hidden;
    transition: all 0.3s ease;
    position: relative;
}

.product-card-modern:hover {
    box-shadow: 0 10px 20px rgba(0,0,0,0.08);
    transform: translateY(-4px);
    border-color: rgba(0,0,0,0.05);
}

.card-img-wrapper {
    width: 100%;
    aspect-ratio: 1;
    background: #f9fafb;
    position: relative;
    overflow: hidden;
}

.card-img-wrapper img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.5s ease;
}

.product-card-modern:hover .card-img-wrapper img {
    transform: scale(1.05);
}

.card-info {
    padding: 16px;
}

.card-title {
    font-size: 14px;
    font-weight: 500;
    color: var(--modern-text-primary);
    margin-bottom: 8px;
    line-height: 1.4;
    height: 40px; /* 2 lines */
    overflow: hidden;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
}

.card-price {
    color: var(--modern-accent);
    font-size: 18px;
    font-weight: 700;
}

.card-meta {
    display: flex;
    justify-content: space-between;
    font-size: 12px;
    color: #9ca3af;
    margin-top: 8px;
}