art looks interesting.
a intro (movie) . why everything is happening or introducing some charakters would be great .
dont give away all the weapons in one tutorial rather bring them later in the levels.. its nothing new or thrilling if you knew everything from the begining.
in the tutorial it would make sense to fight against some roboters rather than zombis if you are talking about a "first approach" .. e.g. say something like we encoutert a problem this is your traning for the real fight or something like that. just more of a story line. the sounds could be better. i just laughed when i heard the zombies die in the tutorial .. :D sorry but i reminds me of button sound if game shows...
why do zombies walk traight a path ? how about more logic like a wall or mountains :D
there seem to be some bugy of the towers sometimes they dont shoot back even if enemys are within their ranges...
even upgraded towers arent so efficently better are troops =( maybe that expains why they are so cheap... rangers are to cheap too since they easy block all paths...
above all why do i have to select a direction? it doesnt change anything... they are still firing behind... why dont you make aa 270 degree attack range rather 360 would make more sense then,,,