Players get nothing. This library has no gameplay code, only the auto-generated compiler file that sets assembly metadata and global usings.
HotCode is an in-editor code IDE for s&box. It gives the user a tree/file explorer, tabbed code editor with syntax highlighting, autocomplete, signature help, find/replace, diagnostics, and an output/console panel. Under the hood it builds Roslyn compilations from the project on background workers, maintains text buffers and undo history, and uses small bits of native interop for UI pixmap work and recycling files to the Windows Recycle Bin.