Nerf Dueling Trees/Flip Targets

if you've watched top shot and seen those dueling trees, and drooled like mad but you can't play with them cuz you're in a place like Singapore which bans firearms, fret not!
Here's a live demonstration:
http://youtu.be/rc8bZGAWSxc
These targets are meant to be in two different colours on both sides, and two competitors will shoot to flip targets to their colour within a time limit.
These targets are designed for stock nerf blasters. I tested them with modified nerf blasters, they should