As soon as you put down the first component, a big red STOP sign will
appear near the bottom of the window. This sign indicates whether your circuit
is valid: it must comprise a complete single, double or triple loop
of connected components.
The sign will turn into a green GO! as soon as your circuit is
valid.
If you include a battery in a valid circuit,
flashing green lines will run along the wires to indicate
that current is flowing.
You can turn this feature off (and back on) by toggling the
Show
Current button.
Once you've placed an item on the grid, you can modify its properties by
selecting it with your left mouse button.
Selecting a battery, for example, will cause the lower-left
portion of the window to display a slider for the voltage of that battery.
Selecting a switch will allow you to open or close it.