Wait wait what does [C] mean? Can I make custom maps for this? Please tell me there's a way to make maps, my friends and I are having so much fun with it!
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The [C] maps are indeed custom, but there's no easy way to load new maps in without creating a modded fork on github and adding them there, or joining the discord (https://discord.gg/dgKVaUKpj5) and submitting a design, usually created in Tiled
There's talks about allowing a custom way to play maps, but no work has been started on it yet.