Valentine's day card
Start with a either a store bought or homemade card and a Light it kit. We're using a newer version of the kit which includes a tilt switch.
You'll need some copper tape, colored paper and invisible tape to hold the circuits in place.
We recommend that you first draw out your circuit keeping in mind all the you know about building complex circuits. Take a look at the example. We used invisible tape to hold down our circuits, this will ensure there is a good connection between the copper tape and the tinned part of the circuit.
Test the circuit to make sure the LED lights up when you tilt the paper upright. You may have to adjust some of the connections to make sure they are secure.
Tape the paper with the circuit onto the card. When your valentine opens the card, the LED should light up!