Zombie Grinder is the debut game of TwinDrills, an indie game development duo made up of Tim 'Infini' Leonard and Jordan 'Jordizzle' Chewning. It's a multi-platform (windows, mac, Linux!) (also Free!) cooperative multiplayer arcade game, reminiscent in style and gameplay of retro games like 'Zombies Ate My Neighbors' and 'Super Smash TV!', but with the added benefit of some newer game mechanics - achievements, ranking, player-customization, rpg style stats and so forth. The game sports a variety of different game modes, from co-operative 'campaign' style levels, to wave maps and even the classic 'pvp' style game modes - deathmatch, capture the 'bag' and so forth. All of these mods are bristling with a variety of weapons and items, all lovingly displayed in Jordan's classic quirky pixel-art style.
Zombie Grinder is a cute and fun game that can keep you busy for about an hour or so--that is, if you are able to play it without crashing during that time. Although that's currently not really a huge problem, having a game crash on you when you blow up some boxes in order to proceed can be problematic in later stages of development. If you're going into it by yourself, I suggest you get a friend to download it as well and play it with you because you won't have half as much fun in this game as you would with someone else. That stands true for most games, but in Zombie Grinder, you will probably enjoy yourself for about 10 minutes before you quit because the waves get so increasingly hard to beat without a companion.
Zombie Grinder has a lot of room for potential, I can see it being fleshed out to include a lot more content in the campaign. It would be nice to go into buildings such as houses or the 24-Seven so you can grab health, food, or ammo left inside; maybe add some neat little details like dead people in the houses with some ammo lying by as inferrence that this person died while fighting. Little details like those can add a lot more life to a small game such as this. I'm sure the developers plan to make the campaign longer. Also, some more variety into the few selection of modes available would be nice. Most of the games you can play are just horde-type games where you fight off waves of zombies for as long as possible. Grab the bag was really fun.