Tilt switches are very simple and a lot of fun. They close (complete the circuit and turn a brick on) by tilting the brick in a certain direction. These work great for alarms when they are connected with a piezo buzzer or LED light.
2 small binder clips
one paper clip
Cut a short piece of a straw and tape it to a brick.
Add a binder clip perpendicular to the straw.
The bump at the end of the binder clip arm should rest right on the edge of the straw opening.
Straighten the outside arm of a paper clip.
Position the curved end of the paper clip inside the straw the exact same amount as the binder clip arm.
Place a small piece of cardboard between the binder clip and the paper clip. Tape in place.
Cut a piece of the straw about one inch long. Insert one leg (sharp part) of your scissors inside the straw and cut.
Tighten the loop of your straw and tape. Wrap in aluminium foil.
Test to see if when the aluminium-foil-wrapped-straw touches the binder clip arm and paper clip if it touches both the paper clip and binder arm and completes the circuit. You might want to do this by adding a power brick and LED brick to make a simple circuit.
If everything works, then tape the straw closed. You don’t want the tape to be able to stick to the foil-wrapped-straw inside the straw. Before you tape the straw closed, add a little piece of tape to the tape itself — sticky side to sticky side. This way that part of the tape won’t be sticky and should cover the straw opening.