http://www.thecodezone.com/games/sandbox/zombiekitten.php
(yeah, I know the page looks horrible because the relative-link to the stylesheet isn't there. It's still playable).
Basically I implemented numbers six and eight from the previous entry. Around level five, houses are eliminated entirely, the number of cats on a level grows more slowly, and the proportion of cats is as follows. . .
After level one, which contains no orange and gray cats, you'll be getting 10% orange and 10% gray cats, and that number increases by 10% per level (orange cats getting priority). That means that around level six there'll be no brown cats left, and by level eleven there should be only orange cats and no houses.
So that means that level four will be the last level with a house, and there will be 31 cats, 30% orange, 30% gray, 40% brown. Level ten should consist of no houses and 55 cats, 90% orange, 10% gray, 0% brown.
And if you can hold your own for that, I will officially declare my game impossible to balance :)
Thanks for the commentary. I do realize that you can take all the time you want during your turn, but when I said that I wanted a game to take "five minutes max", I meant during normal casual play. You can, of course, have a game that lasts three hours by simply starting the game, going out to a movie, and returning later, but that's not really what I'd consider interactive play.
I'm really trying to avoid doing the "auto-standstill after five seconds" rule, because it's going against the turn-based "spirit" of the games. I do want the game, despite the theme, to be something that you can play leisurely while sipping your morning coffee.
I just hope you haven't made it too hard for everybody else.