It is multiplayer game that is playable over a network using UDP.
Download the protobuf source release (version 3.6.1) then go to the java directory and traverse the com, google, protobuf folders until you reach the java files. In the directory:
$ javac -cp protobuf-java-3.6.1.jar -d . *.java
Copy the contents of the com folder that was made into the repository folder with the same name. Go to the java-protos folder of the repository and compile:
$ javac -cp ../protobuf-java-3.6.1.jar -d . *.java
Copy the contents of the proto folder that was made into the repository folder with the same name. Compile the main java files in the root directory of the repository:
$ javac *.java
The ending directories of the root folder would look like this:
com/
google/
protobuf/
<class files>
java-protos/
player.proto
PlayerProtos.java
tcp_packet.proto
TcpPacketProtos.java
proto/
<class files>
.gitignore
protobuf-java-3.6.1.jar
README.md
*.java // all java files needed
Then run the Main file.
$ java Main