Very interesting game idea ! I had a great time playing this.
The puzzles aren't very balanced though, since you can often neglect one player and try to go straight in one direction with the other and eventually you will merge them. Sometimes this doesn't work out but you can still put one in a corner and try to reach it with the other by using directions that are blocked to the first one.
This is for levels 1, 2, 4 & 5. I think level 3 is much better !