Well, that was the reason why I made this so that your friend can still make her/his wish on the spacial day.
The project is the result of improvisation, made of everything I could find in my office desk in 30 min. (I have a bit of strange selection on my desk.. but do not ask..) The principle is very simple. The connection between battery and LED is going through the tilt switch, which is placed vertically on the blow target paper. As you blow the target, it gets tipped over and the tilt switch lays horizontal, resulting to disconnect the connection between LED and the battery.
Step 1: What you need
-1 button battery (3V)
-1 tilt switch
-some conductive thread (can be wire)
Step 2: Step 1: preparing the tilt switch
Make a loop at the end of each legs, and connect conductive thread by simply knotting them. You can also solder normal electric wires instead of using conductive thread.
Step 3: Step 2: prepare the target paper
I have simply folded a small paper (I cut out the sticky part of a post it paper) into 90 degree, so it can stand.
Place double sticky tape on the paper and place conductive thread, then place a button battery. remember which direction you placed the battery.
Step 4: Step 3: place tilt switch on the paper
Then place one of the conductive thread connected to the legs onto the battery facing out, and tape them together. Make sure that the connection between battery and threads are good and stable.
It should look something like this on the picture. make sure that tilt switch is getting the on/off as you tip the target paper. If not, adjust the placed angle of the tilt switch.
Step 5: Step 4: prepare the LED candle
Make sure that the direction of LED is correct. In general, LED's longer leg should be connected to + and shorter one to the -.
In this example, I placed button battery with + facing the paper, so the thread coming directly from the battery goes to my LED's longer leg, and threads coming from tilt switch goes to shorter leg of LED (-)
After making the connection, I taped them inside the candle paper, so that it does not touch inside.
also, you can place some paper with target mark so that you do not see the switch and battery and you know where to blow!