Very interesting puzzle-game !
At first I was very confused because the "desappear when in cross" is very unintuitive as well as the fact that you can jump over your clone. I think this mechanisms must be more smoothly introduce in easier levels at the beginning of the game ! But once you understood the rules, it become very challenging and interesting as the gameplay is original and you have to figure out some ways to move on the map without leavind behind all your clones !
I still want to solve Observer 2.0 ^^