A simple shape that has been constructed at the apex and the line, move the vertex, by changing the position every second, you can play the animation. Please be first move by touching the vertex Any. And Touch the right triangle "▶▶" button, to advance one second. Also, move the vertices freely. Touch the left triangle "◀◀" button, to go back one second. Finally, you can play the animation by touching the right play, "▶" button.