dotnet/roslyn ? reverse-engineered prompt

Build me a simple Roslyn based code analysis playground that works for both C# and Visual Basic.

I want to paste code into it, see compiler errors and warnings right away, and get a few helpful bits of info like syntax highlighting, symbol info, and a simple tree or outline view of the code. It should feel like a lightweight developer tool for understanding code, not a full IDE.

Please keep the experience clean and practical, and reuse whatever is already in this repo where possible. If you need current Roslyn or .NET docs to make sure the setup is right, look them up online.

When you’re done, I want something that builds and runs easily, with a clear way to test that the analysis features are working.