This is a simple light unit, with a less-than-simple switch. To turn it on, you... er... turn it upside down!

Step 1: You Will Need

1 tilt switch. Any variation works
1 battery (CR2032 in my case)
1 battery holder for the above battery
1 LED, suitable for the battery (most are)
1 glass pot
Some wire
Some blu-tack, or hot glue

Step 2: Check Your Equipment

First test the components by holding the legs of the LED on either side of the battery. In one orientation, it should be lit. The short leg of an LED is negative, and is placed here against the 'dimpled' side of the battery.

Step 3: Make the Circuit

Next, solder the components in series: battery holder negative, to LED negative, then onto tilt switch and back to positive. I used stiff plastic coated wire soldered onto the tilt switch connectors so that I could manoeuvre the switch into a suitable position.

Place the battery into the holder, and blu-tack or glue it to the lid of the pot. You should find that, when the lid rests on the table, the light comes on, and when turn upside down it is off. If not, bend the tilt switch, via the stiff wires, until that happens. I found it easier to hold the lid firmly on the desk with one hand, and move the switch with the other, until it lit. In this way almost any other position will turn the light off.