Now, with what you know, you can make BASIC a powerful tool. Something that your program should have is a good interface. The GUI stands for Graphical User Interface. Your GUI should match that of other applications/programs as much as possible, which makes it much easier for the user. As said in the miscellaneous section, you must pretend that your user is incredibly dumb. This will deal with all the possible errors they will make, and will reduce the length of manuals/tutorials. So, let's begin making advanced menus.
First, you will want your program to clear your graph screen, and remove the axes, so it's not showing up behind the menu. Then, you can use the Line( command to draw the lines in your menus. Using the text command, you can then draw text. How do you use this? Well, Argon, Sirius, Polaris, and Chromium use nothing except for lines and text to make all their menus. Sirius and Argon use something called Dynamic Menus in conjunction with this, which will be explained in the next section. How do you find out where to put the lines? At the place where you want to insert the lines, put the "Input" command. Then, run the program. It should stop at the place where you put the "Input", and show you the coordinates. Write down the coordinates, then press "On" to break the program. Press "Goto" and replace the "Input" command with the lines using the coordinates you wrote down. Some menus can be incredibly simple, and some can be complex. Chromium's menu is set up in about 8 lines. Argon's however, gets set up in about a hundred lines.
How do you get user input? Here's an example menu: