Controls:
Press b to switch to ball editing mode. Left click to place, right click to remove.
Press s to switch to stick editing mode. Left click to select a ball to attach it to. Left click two balls to place the stick. Hold right click and draw across a stick to remove it.
Press p to switch to pin editing mode. Click a ball to toggle if it is pinned in place or not.
Press g to switch to grid editing mode. Click and drag to create a grid of balls between the two positions. This is useful for simulating cloth.
Use the scroll wheel to change the spacing of balls in edit mode.
Press space to toggle between simulating physics and editing.
While in simulation mode, you can left click a ball to toggle if it is pinned and hold right click and move across a stick to remove it.