Forgot to add that that resistor size is just for the 2 LEDs connected to one 9-volt. You should be able to wire 2 more LEDs to that set up and leave off the resistor, but I haven't tried that yet. I've been just making pairs to use in different props. You can buy different battery packs for different amounts of batteries, but you'll need to figure out what resistor to buy for the amount of batteries vs. the amount of LEDs you want to wire into one unit. I'm going to try to wire a bunch of pairs of LEDs together to one big battery pack to make a bunch of eyes to hide in the bushes. They also sell blinking LEDs so I might use some of those too.

***Trick or treat. Smell my feet. Give me something good to eat.***