* Catwalks are an upgrade to lattice; instead of just a framework of wires its a mostly solid grid walkway.
* They are semi-transparent so you can see wires/pipes below them a bit.
* Smoothly auto-joining sprites to look proper.
* Constructed by upgrading lattice; like lattice it will stop you falling if build over an open space.
* Changes from Eris: Converted << to to_chat(), fix redraw on Destroy(), Fix color macros in text.
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