Pipe system water

Does anyone have any idea of how to achieve an effect like Piperoll here - youtube.com/watch

I'm guessing a grid with series of sprites that can be rotated 4 ways, but not sure how you would do the following:

1) Detect whether a connection has been made?

2) If connection has been made then how do you mask the water so it progresses through the pipe?

Many thanks for your help

Simple way:

Use extra image points on the sides the pipes touch, check if multiple imagepoints have the same x and y coordinates (if so set variable connected to 1) Make an animation of the filling of the pipes with water. If connected is 1 and animation is filled with water set animation to fill with water..

Something like that?

This was just an imagining-exercise for me though, break up the things you want to happen into small pieces and figure out how to connect those pieces..