def get_portals(entries):
    """Create mapping of portal entrances from entries."""
    portals = {}
    for portal_name, locations in entries.items():
        if len(locations) == 2:
            (location1, level_change1), (location2, level_change2) = locations
            portals[location1] = location2, level_change2
            portals[location2] = location1, level_change1
    return portals