After replacing some old window blinds, my 4 year old had taken a shine to one of the old clear twisty-stick thingies. I asked to look at it and told her “You know, I might be able to do something with this….” Before I finished the thought, she said exactly what I was thinking.
“You could wight it up wif some LEDs!”
Drilled a small divet in one end and inserted a blue LED, and hot glued it in place. I grabbed a length of PVC to be the hilt, and the interior was just wide enough for a pair of AAs. Soldered a wire to one end of the LED and duct-taped that to the top of the first battery. Soldered a resistor to the other end, then a wire from that that slid down to the bottom of the hilt and bent it up the side. Duct taped another wire to the bottom of the second AA, and up the side to hang loose. Wrapped this all up in common silver duct tape.
The second wire is bare at the one end. If she presses it down to the duct tape the circuit closes and it lights up. Very simple design. I’d have put a button switch in there but I didn’t have anything that’d do the job properly, but this setup will probably be more rugged for a 4 year old. It’s not especially bright, but it’s more than sufficient for playing around with.
Now to keep her from smacking the cats with it.