The idea of Five Letters came from InteractAndPlay.
Five Letters is basic. You turn the five letters in the post above yours into a sentence that makes sense. An example is TIAGE into This Is A Good Example. Then you state 5 more letters. InteractAndPlay made a generator for the purpose.
The two modes are Classic and Metric. Classic is the same as what is above. Metric is 10 letters. The only rule to Metric is you cannot have the same letter twice.