Illustration of <a href="https://en.wikipedia.org/wiki/Neighborhood_(mathematics)" class="extiw" title="en:Neighborhood (mathematics)">en:Neighborhood (mathematics)</a>
<a href="//commons.wikimedia.org/wiki/User:Oleg_Alexandrov" title="User:Oleg Alexandrov">Oleg Alexandrov</a>, <a href="//commons.wikimedia.org/w/index.php?title=User:Crazytonyi&amp;action=edit&amp;redlink=1" class="new" title="User:Crazytonyi (page does not exist)">User:crazytonyi</a>
Neighborhood_illust2.png; SVG hand written. Based on Oleg's PNG.  Threw out his SVG rendering with Inkscape, save colors and font.