In sandbox mode, moving the mouse (or touching and dragging along the screen) previews the Voronoi diagram that would result from placing a site there.
Limit sites to a grid with a spacing of pixels between points
Limit sites to one dimension
Play against computer*
Quarantine mode (minimum distance between points)
*Playing against the computer only works in sandbox mode currently and can be started on either player's turn (red or blue). The computer player uses a simple greedy algorithm to pick its next point, looping through a grid of possible locations (with a spacing of 10 pixels between points to keep it reasonably fast) and choosing the one that maximizes its area after that turn.