Chip's Challenge

So some guy comes along and asks you to remake Chip's Challenge for him.  He lets you do it in whatever language you want.  You can organize the code however you want.  The catch is this:

You need to be able to add new tiles easily.

How do you approach this /prog/?

>>3

Easy as in when you add a new tile:

-Minimize number of places you have to declare the new tile type
-Not worry about every other type of tile in existence
-Still be able to easily deal with certain tile-creature interactions (block x water, glider x water, etc)