After playing for little over an hour i have completed all the missions and then you unlock extreme mode and endless mode. There is however replayability in this game. In order to conquer extreme mode i think you would need some of the higher up level guns so you have a small grind to get there of a few hours. Nothing highere than level 20 im at 10 in an hour so there is that.
The levels all playout the same really with small things to change them defend something static and your quite confined to an average size area to do it. There is little bits of cover out there and things to climb for height but there poorly implented and you can just stand in the open if you want to.
There no crouch or prone just stand and jump. No sights just right click and it makes the 3rd person view zoom in a little. Except the sniper rifle but other weapons have sights on them.
But there is an arcade feel to it as you can achieve headshots and blow bodys to pieces for extra points if you want.
The points become cash for all your upgrade some cosmetics ones and some very basic buying of weapons but no customized weapons just as ther come.
It plays nice and graphics are ok at best running in 1080p on fantastic setting the (highest one.
Overall lot of mindless fun to spend on a quick break or mindless afternoon but nothing more. No story no depth just ARCADE FUN.