This short collection of projects - some useful, some instructive, and some amusing - can be made for around 10 UK pounds (16 US dollars). The estimated cost does not include an enclosure (box). All of the projects are battery powered, so are safe to build.

Hocus-pocus, get your Halloween party off to a shriek!

This is one of those novelty projects that leave the constructors with full scope to use their imagination and skill. The essential idea is that the circuit is made to look like a fearsome (or perhaps foolish) bug. In the light, the bug just stands there looking fearsome (or foolish). As soon as the light level falls below the preset level, the eyes of the bug start to glow and it emits a weird wailing sound. This continues until the light is switched on again.

This is only one of several possible applications for this circuit, some bug-related, some not.