You can use the library by copying the file into your `screeps` code directory and then using `require` to load it. Downsides to using more code (whether it's yours or an external library)- You have a 2mb limit on how much source code you can have. When you `require` a library that isn't in the require cache you have to pay for all the parsing times. Basically you should be fine using smaller libraries, but should avoid the larger ones.