To get some feedback from the audience we also created a topic on reddit and gained a lot of interesting commentaries. Because of them we saw some weaknesses of our game and made some updates, but of course work is still in progress.
For now we added little animation to zeppelins, so they look more vivid and made bullets twice larger. And this surprisingly changes the feeling of the game, yet it's a small change.
Now we are working on adding Time Attack mode, where the player is given only 30 second from the start, and he must get as much time as he can.