yea expert is definitely hard, depends on luck too because when the Tank appears, it almost gg

The farthest ive been is that room with the machine gun but got overwhelmed by the zombies.
Wondering if this game is worth getting, seems like theres only 3 levels more and level 1&2 are really short. Aside from 3 extra levels and verses mode what else is there? is that it? if so... not worth $50 lol