The device is based on a PIC16F88 microcontroller. The sleep mode of the PIC is used for standby, negating the need for a power switch. The PIC simply records the last state of the metal ball switch and then uses the opposite of this as a trigger for wake-up.
If the metal ball switch isn't shorted, the device uses in the order of nA for standby. If it is shorted, it uses about 15uA. Either way, the batteries (3xAA) should last a fair amount of time, given my child was bored with it by 9AM on Christmas day!
An ICSP port is provided on the PCB to allow for easy re-programming should I have the time to develop some new LED patterns.
Since the batteries will last a reasonable amount of time, I simply glued the container shut with epoxy resin, making it impossible for a child to get anything out of there.
The box was only about $2.50, so it's not the end of the world if it does have to be destroyed to change the batteries.