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将msd 模组包含进mtr 内
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希望默认轨道变成即将发布的立体轨道功能,并在存档升级时自动替换为立体轨道

MSD exists as a separate addon so the core mod won't be cluttered with literally everything related to railways. Also, 3D rails have been added to the main mod in 4.0.0.