What do you think of my idea? How do you think i can improve it?
Simplify it. The system has already become too complicated for its own good. If you are really interested about improving it, then make a prototype which can be played and tested.
Is there a situation in your game, when it has no legal moves? In games like this: Tetris, Match-3, Lines, so on, there is some kind of no-legal moves situation. Usually it's where game ends. I think adjusting rules, so such situation arises may improve gameplay. For example some idea: You can rotate block only if some block pops down during that rotation (either rotating or neighbor). Blocks pop down if at least 3 their sides match sides of neighbor squares. And, yes, you can't exchange color on sides. It's untested, but may serve foundation for more refined version of rules.
I think requiring variety of food (same food heals children less over time) and making children require food less often as they grow would somehow help. Also you can add some visual hints pointing to food of specific kind, so you can visually find food.
The first check: can the rough game prototype be made using this concept? If not, then it is a junk and should be thrown away without any back thought.
Compare:
The game will feature four garrisons set in a hor. line with each defender in the garrison. With each garrison a ver. line is associated, where monsters travel to a garrison. Each defender has a unique attack pattern on the line with different damage type done on different distances from his garrison. Each monster has an armor which deflects certain damage type. If defender attacks monster without deflection, monster is killed. If defender attacks the line and monster or monsters deflect his attack, he is harmed instead. If monster reaches garrison, game over. Player has 2 actions: swap 2 defenders, or order any 2 defenders to attack. Monsters spawn on the line and move forward between turns
And
The game will feature 3 races with unique abilities, the graphics will be cartoonish and dark. It will feature extensive upgrade system. The setting is based in year 2067, where humanity had survived nuclear winter. Player will have to pay attention to the screen, because it will determine life or death. Action will be fast-paced. Deploying and moving units will involve great strategical thinking as well ability to micro-control. After the battle player will get XP to level-up his character, which he can then deploy to assist his units.
Play Ninja Gaiden I and II, it has enemies which always spawn when screen enters certain area, and despawn when it leaves the screen. You can see how such behavior actually affects gameplay.