drag mouse to draw

drag mouse and hold "s" key to draw with springs

FIXING

drag mouse and hold "f" to fix particles

press "x" to unfix particles only in Z axis

press "y" to unfix particles on all axis

GRAVITY

press "g" to turn on gravity in -Z direction

press "c" to direct gravity in z direction

slowly drag mouse in left or right direction and hold "r" to direct gravity in left or right direction.

slowly drag mouse in up or down direction and hold "t" to direct gravity in up or down direction.

press "h" to turn off gravity

VISUALIZATION

press "b" to refresh screen

press "k" to kill particles, then can also press "b" to clear screen