My thoughts on this game are as follows.
Personally I'm a huge fan of the open map I can explore, lots to look around and many areas to put Zombies in. Not only that - The sprint feature also makes it easy to quickly look around the vast open map, so I'm happy you decided to add that.
My only complaint however is the Screen Size. It makes it hard to fire with the small screen, my mouse constantly going outside of the gameplay window.
You did a good job on this, so congrats.