Dead frontier is the best web browser zombie mmo. Challenging, hard, addictive and fun. I have many friends that like mmos but quit because they cant keep their char healthy, or nourished. Personally that game is amazing. Huge world, different zones. Many kinds of zombies, bosses and extreme hard bosses (aka flame wraith, and black titan, and flame titan) need to keep your player nourished find food of your lvl, medicine, armor, weapons, ammo, play with friends, boss raiding, looting the city, just an amazing game for me. Check it out.