I thought this tower defense and kingdom balance was a clever idea.
My first playthrough was confusing due to lack of resources after dropping towers that shoot. On more careful inspection of the options, I instead placed a lot of huts and trees to get the resources rolling...then the game was easy. At first I thought it was important to remember the skills of each hero color, but in the end, the color was the most important aspect to address and boost kingdom happiness. With proper resource generation foundation there was not much concern.
May have felt more urgent if buildings expired/fell down and you needed to replace them to maintain the resource flow and the enemy snakes did more damage to all item/heroes in play.
The concept is great and a good start to something that could go a long way.