The game belongs to the genre of Tower Defense.
Purpose of the game: retention onrushing enemy.
There are many types of turrets with different properties. Almost all of them have 10 levels ("Flame Turret" has 20 levels.)
All turrets are carefully balanced among themselves, so there are no useless turrets. Each turret performs its irreplaceable function in collective defense. Some turrets are not effective in some missions, but in other missions they can be extremely useful. For example, splash attacks of "Meteor Turret" and "Power Gun Turret" qualitatively differ among themselves, the "Meteor Turret" is a more specific turret than the "Power Gun Turret", but it can help to refrain a very dense stream of creeps, if it is located in a felicitous place. Which turrets to build and where to place them - you decide.
You can change the priority for each of the turret (nearest,weakest or strongest target.)
In this game it is more beneficial to upgrade the constructed turrets as possible, than to build new ones.
To perform difficult missions, you need to have a good tactical and strategic abilities,
and the ability to make quick decisions and adapt to changing conditions.