Extrasensory Perception 2 is an ingenious gimmick that does all the work for you, you write on the board before the symbol is thought of, once the prediction is written the chalk is left and nothing else is written, the ingenious mechanism is activated imperceptibly you only have to dedicate yourself to the presentation, remember once written the symbol the blackboard is all the time in sight, no strange movement is made, the chalk and the blackboard are all the time in sight.