Using diodes as switch regulators...
Battery is connected to the first diode via a switch (touch/key), then to the next diode and to the load (bulb). Another switch cuts from the centre of the diodes to the battery. An finally a third switch is connected directly to the load.
When the first switch is closed, current flows and the bulb lights. If the second switch is closed, it is directed to the second diode which makes the bulb brighter. And lastly when the third switch is closed, the bulb lights more brightly because it now has a direct contact with the battery.
