The type or namespace name 'SFML' could not be found

[Smie.Grin]

Hello, board! I have had great success and fun with SFML, and I'm hoping to try it out with the more "modern" C# language.

I have successfully compiled and run simple programs using other nuget packages such as the Newtonsoft.Json package, but I have met difficulty with the SFML Nuget packages.

With the attached minimal files, I run dotnet restore && dotnet build and I get the following error:

  Restoring packages for /home/smie/Documents/sharpC/testSFML/testSFML.csproj...
  Generating MSBuild file /home/smie/Documents/sharpC/testSFML/obj/testSFML.csproj.nuget.g.props.
  Generating MSBuild file /home/smie/Documents/sharpC/testSFML/obj/testSFML.csproj.nuget.g.targets.
  Restore completed in 176.49 ms for /home/smie/Documents/sharpC/testSFML/testSFML.csproj.
Microsoft (R) Build Engine version 15.8.166+gd4e8d81a88 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  Restore completed in 33.98 ms for /home/smie/Documents/sharpC/testSFML/testSFML.csproj.
main.cs(8,24): error CS0246: The type or namespace name 'SFML' could not be found (are you missing a using directive or an assembly reference?) [/home/smie/Documents/sharpC/testSFML/testSFML.csproj]

Build FAILED.

main.cs(8,24): error CS0246: The type or namespace name 'SFML' could not be found (are you missing a using directive or an assembly reference?) [/home/smie/Documents/sharpC/testSFML/testSFML.csproj]
    0 Warning(s)
    1 Error(s)

Time Elapsed 00:00:02.01

This is my system information from dotnet --info:

.NET Core SDK (reflecting any global.json):
 Version:   2.1.401
 Commit:    91b1c13032

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  18.04
 OS Platform: Linux
 RID:         ubuntu.18.04-x64
 Base Path:   /usr/share/dotnet/sdk/2.1.401/

Host (useful for support):
  Version: 2.1.3
  Commit:  124038c13e

.NET Core SDKs installed:
  2.1.401 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.3 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.3 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

I've been searching for a while over google and through these forums, but I still haven't found any solution.

Thank you for your help! Let me know if I can provide any helpful information.