During the Vietnam War (and other wars as well), prisoners sometimes used tap code to communicate with each other. It's easer to learn than Morse Code but quite a bit slower.
The letters of the alphabet are arranged in a table. You first tap the row number of the letter you want, then the column number.
If you are wondering why there is no letter "K" it is because they wanted to be able to fit the alphabet into a 5x5 table (25 locations) so one of the letters had to go. The "K" sound can be made with a "C" so you are supposed to substitute "C" for "K".
For more information, see the Wikipedia article http://en.wikipedia.org/wiki/Tap_code
This project can use either the microphone or the space bar to generate a "tap". Try clapping your hands or tapping on the back of your laptop and see if it works for you. The triangles show which row or column you are currently on, the red triangle is the one that is active.
The project is currently set up for a one second pause to switch from row to column and a 4 second pause marks the end of a word.
If you mess up while sending a letter, just tap more than 5 times and the process will reset.
Use the Green flag to reset the sentence.
The table image I got from the Wikipedia article and then modified to make the grid rectangles consistent.
The jungle image came from Wikimedia Commons.