Compound curve from corner 1, start of tunnel
<a href="//commons.wikimedia.org/wiki/User:Useddenim" title="User:Useddenim">Useddenim</a>
2023-04-24
Own work based on: <a href="//commons.wikimedia.org/wiki/File:BSicon_tkSTR2a.svg" title="File:BSicon tkSTR2a.svg">BSicon tkSTR2a.svg</a>