First off, great game. Already got me hooked. Finished the demo on both maps a couple of times now, and I've only been playing for 3 days.
First of a suggestion to the user interface. It would be great to have a way of seeing how much water and food is consumed by your current population. Makes planning for the dry season (which is a great concept for a beaver colony based game) a lot easier. Could add to that a way of seeing how much storage capacity your dammed off basin has with it's current consumption off water pumps, crops, forests etc. (don't actually know if irrigation is c