The GUI in this program is Text-mode based. It is Non-BGI. So, it isn't that very appealing to the eyes, yet reasonably user-friendly & elaborate to use. Download the code & read the documentation to understand the logic of the Text-based GUI of this program.
PS : BGI can be used to develop an actual Graphics interface that is detailed & developed, for this program.
"Don't take life too seriously; No one gets out alive."