#resizer {
    width: 20px; /* Increase hover area */
    background-color: transparent;
    cursor: col-resize;
    flex-shrink: 0;
    position: relative;
    margin: 0 -10px; /* Center the visual element in the gap */
    z-index: 10;
}

#resizer::before {
    content: '';
    position: absolute;
    left: 50%;
    top: 0;
    width: 10px; /* The visible line */
    height: 100%;
    background-color: var(--border-color);
    transform: translateX(-50%);
    opacity: 0;
    transition: opacity 0.3s ease, background-color 0.3s ease;
}

#resizer:hover::before {
    opacity: 1;
    background-color: var(--highlight-accent);
}

body.resizing {
    cursor: col-resize;
    user-select: none;
}