:root {
    --bg-color: #f8f9fa;
    --text-color: #212529;
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --card-bg: #ffffff;
    --border-color: #dee2e6;
    --shadow: 0 2px 4px rgba(0,0,0,0.1);
}
body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    margin: 0;
    padding: 20px;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}
.hcm-container {
    max-width: 1400px;
    margin: auto;
    display: grid;
    grid-template-columns: 300px 1fr;
    gap: 20px;
}
header {
    grid-column: 1 / -1;
    text-align: center;
    margin-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 20px;
}
header h1 {
    margin: 0;
}
.panel {
    background: var(--card-bg);
    padding: 15px;
    border-radius: 8px;
    box-shadow: var(--shadow);
    flex-basis: auto;
}
#filters-panel {
    overflow-y: auto;
}
.main-content {
    display: flex;
    flex-direction: column;
    gap: 20px;
    min-width: 0; /* Prevents flex items from overflowing */
}
.filter-group {
    margin-bottom: 20px;
}
.filter-group h3 {
    margin-top: 0;
    font-size: 1rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 5px;
}
.filter-group div {
    max-height: 150px;
    overflow-y: auto;
    padding-right: 5px; /* Add some padding to avoid scrollbar overlapping content */
}
.filter-group label {
    display: block;
    margin-bottom: 5px;
    font-size: 0.9rem;
}
#search-box {
    width: 100%;
    padding: 8px;
    margin-bottom: 15px;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    box-sizing: border-box;
}
#system-list {
    max-height: 400px;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 5px;
}
.system-item {
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    margin-bottom: 5px;
    cursor: grab;
    background-color: #f1f3f5;
    font-size: 0.9rem;
    text-align: center;
    transition: background-color 0.2s;
}
.system-item:hover {
    background-color: #e9ecef;
}
#comparison-area {
    min-height: 200px;
    border: 2px dashed var(--secondary-color);
    border-radius: 8px;
    padding: 15px;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 15px;
}
.comparison-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 15px;
    box-shadow: var(--shadow);
    position: relative;
}
.comparison-card h4 {
    margin-top: 0;
    font-size: 1.1rem;
    color: var(--primary-color);
}
.comparison-card ul {
    padding-left: 20px;
    font-size: 0.9rem;
    margin-bottom: 0;
}
.remove-btn {
    position: absolute;
    top: 5px;
    right: 5px;
    cursor: pointer;
    border: none;
    background: transparent;
    font-size: 1.2rem;
    color: var(--secondary-color);
}
#timeline-view {
    position: relative;
    height: 120px;
    border-left: 2px solid var(--secondary-color);
    margin-left: 50px;
}
.timeline-marker {
    position: absolute;
    left: -5px;
    width: 10px;
    height: 10px;
    background-color: var(--primary-color);
    border-radius: 50%;
    cursor: pointer;
}
.timeline-marker .tooltip {
    visibility: hidden;
    width: 160px;
    background-color: #333;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px;
    position: absolute;
    z-index: 1;
    bottom: 150%;
    left: 50%;
    margin-left: -80px;
    opacity: 0;
    transition: opacity 0.3s;
}
.timeline-marker:hover .tooltip {
    visibility: visible;
    opacity: 1;
}
.timeline-year {
    position: absolute;
    left: -60px;
    width: 50px;
    text-align: right;
    font-size: 0.8rem;
    color: var(--secondary-color);
}
#export-buttons {
    margin-top: 15px;
    text-align: right;
}
#export-buttons button {
    padding: 8px 15px;
    border: none;
    border-radius: 4px;
    background-color: var(--primary-color);
    color: white;
    cursor: pointer;
    margin-left: 10px;
}
#export-buttons button:hover {
    opacity: 0.9;
}

@media (max-width: 768px) {
    .hcm-container {
        grid-template-columns: 1fr;
    }
    #filters-panel {
        grid-row: auto;
    }
}