very difficult
graphics are good and clean, the game-idea with the plain is nice, too. but there are two things i really dont like:
1. the gameplay is fuzzy and cause...
2. ...that your balancing is very bad. all over you have got 40sec (no matter how many characters you have to fill).
the result is a very short motivation for this game.
maybe you give more time to fill the characters but a limited stock of smoke so you have to think more about how you use it. at this point you can use the "trial and error"-principle to make this game.