The Buttons on the screen should not be just rectangular, they should be shaped.
If you ever tried to make shaped buttons with any programming language, you know it is hard.
I found an unusual and very easy way to make buttons in any shape you like.
You can see the result in the attached zip file (just unzip and open the "index.html" in your browser)
or here on www.openprocessing.com
Step 1: Paint the buttons
The dimensions should be the same as the window size of your program or applet.
Then you copy the buttons and fill the buttons with different colors.