Keep in mind that because the levels are randomised every time you start one, you can simply press the left and then the right arrow key to get a new level on the same level number. Very helpful for when you're hopelessly stuck on one particular level.
I especially like the fact that the spells and equipment you get are randomised every time, forcing you to think smart and make the best of what you've got time and time again.
Tip for the hard badge: get some nice air on the far end of the wires and just stay there, punching and bouncing. The enemies will come to you, and no weapon they can use is really useful for damaging you, as you're moving all the time. Often, you will knock them into the pit almost immediately. Take care to stay away from the pit yourself by moving to the other end of the wires when the enemy is on them too. I got 20 kills with barely any effort this way.
"Thanks for letting me stay here, Jackson! Oh, and if you don't mind, I'm now going to take everything you own and be on my way again. Nice meeting you!"
A little tip for the hard badge: finish a game on 'pretty easy' mode and then train all skills of 5 of your survivors to the max. When you've done that, leave the city with those five and start in a new city, only this time on 'seriously hard' mode. All of their skills will be retained (which means they're experts in everything you want to use them for), reducing the hard badge to a cakewalk.
@Neenja: The Sphinx was created by Izzy, and she also wanted a memento of her, so she got Izzy's hair. When Izzy was fading, however, the Sphinx was afraid she would fade away as well, so she did everything she could to stop this from happening. While doing this she created the wolf and she tied it with the hair to avoid any incidents. Lazarus explains all of this when you get trapped by the cultists.
1st playthrough: No orange dudes spawned; 2nd playthrough: The orange dudes froze; 3rd playthrough: They froze again; 4th playthrough: I was finally able to finish it. This is a good game. It just has too many flaws.
 "Thing-Thing 2"){kind=icon}
 "The Very Organized Thief"){kind=icon}
 "loops of zen")
 "Cardinal Quest 2"){kind=icon}
 "Road Of Fury 2")
 "Chaos Faction 2")
 "Pandemic: American Swine")
 "The Last Stand: Union City"){kind=icon}
 "Rebuild 2")
 "Rogue Soul 2")
 "Soccer Physics")
 "Last Legacy: Null Space")
 "The I of It")
 "Pursuit of hat 2"){kind=icon}
 "Collapse It")
 "Glean 2")
 "The Everloom")
 "Death Dice Overdose")
 "One Step Back")