Spend long hours on this one
This is a fairly simple game, but the killing gets you hooked on it for hours. Although I feel that there are things that could be improved.
The upgrades to the weapon only adds to their ammo clip. Sure, it helps from the beginning of game to mid game. Once you get to 3000+ kills, the amount of zombies pouring out is pretty overwhelming for the ammo clip given. Added damage should be included.
To add on top of that, the zombies' life gets longer as you progress with the killings. At 3000+ kills, to kill a normal zombie, it'll take me 3 hacks of the machete. At this point of time, machete is pretty much my main weapon because I ran out of bullets really fast (The zombies can take alot of bullets by then) and I have issues with some of the guns.
There are weapons with too long cooldowns, it does not feel so in mid game. But when it's at the latter part of the game, Shotguns and Sniper Rifles are useless. Actually, I stopped picking up Sniper Rifles since mid-game.
Sniper Rifles are slow, and they do not really penetrate much, roughly only about 3-4 zombies? And their barrels are so long, I cannot shoot enemies in front of me. This is a big deal in later parts of the game. This is the worst weapon in the game.
Miniguns are useful despite them having long barrels like Sniper Rifles, they really could dent the population of the zombies on your screen. The bad thing is, they slow you down, way too much in my opinion. It's really impossible to run away from the Running Zombies once one of them bites you. You gotta lose that Minigun or summon help from above. Which sucks really since they do not drop that often. At least in my experience.
No matter how skillful one is with the machete, you'll still find yourself relying on the weapon crates. As the stage progress, it takes too many slashes of the machete to kill a zombie. Either the machete's swing speed/damage should be heightened.
To be fair, I did not get the last 3 weapons unlocked, maybe those final 3 weapons are God-like? And the hordes don't look so overwhelming anymore.