As a twin stick shooter, Zombies is extremely easy to pick up and play for a high score. The 8bit title screen certainly helps to encourage that pick-up-and-play feeling. I've only played by myself, but I find it interesting that four-player multiplayer is also available. I'd really like to try it out for myself, but I really don't know when I'll get that chance, seeing as I don't know anyone else on Xbox Live that could play with me, or anyone who can spare the time at the start of the school year.
The different enemies, the send up of Geometry Wars, and the color changes, flashing lights, and changing backgrounds help to keep the illusion of changing gameplay, but the flow is generally the same. Of course, the screen is going to get more crowded and switching to the appropriate weapons will be key. The ammo, weapon drops, and power ups all seem to be fairly well balanced, but there is one thing that's bothering me.
Honetsly, I get the whole indie vibe, and while independent games aren't the easiest to get ahold of, I try my best to keep an eye on the development. Still, the low budgets can affect a few items on the development checklist. Case in point, Zombies' music is terrible. Starting out in a garage band and morphing as it goes along makes the title song interesting at best, and annoying and grating at its worst... which is most of the time. Do I get it? Yes, but I just don't want it.
I'll try to remember to post a link to my full review when it goes up on gamerevolution.com.