in response to "we have no score designed. just to pass the levels." from the developer.
But you do you have score system to earn the most "vials" per level and get the most rewards and then be able to unlock everything, which cant always be done by simple means
for example: level 4 where you have to use all your moves to win there for earning no vials with out using items which are finite and force us to pay cash to get more
something like this is the simplest example of a money grabber game on facebook
in response to the developer's reply "you can enjoy it without any pay. there is many bonus. hope you like it." every other facebook game like this can be "enjoyed" with out pay doesnt mean it will be nor does it mean the game will be fair most games like this require you to spend cash to get optimal scoring