the game has two stages. The first is simply surviving, which takes a few attempts. The second is surviving with style. As the scoreboard shows, there is a method to getting a 5000+ score. However, there's a new degree of skill required for each 1000 points above that.
I'm still trying to figure that one out. I've been using a dry-erase board to keep track of leveling, but it's tough to figure out how to time your changes in strategies for each day/night.