[b]Note: [/b][br][list][*]To drag the point in the grid (where [math]z=0[/math]), simply move it. [/*][/list][list][*]To move the point UP or DOWN, click the point first and then drag it up or down. [/*][/list][list][*]Click on the point again and then drag it to move it LEFT and RIGHT again (and keeping it at the same level above or below the grid). Click again to then move it up and down, and so on. [/*][/list]