Thanks for trying out the game!
As for the being small for hitting buildings part, you actually grow automatically. If you lose blood you get more Monzillas (limited to 3 at a time), but in order to hit the taller buildings, there is a different mechanic to it. Most of the time the other AI-Monzillas will break them for you, but not always. So you need to either survive long enough to grow (usually a couple of seconds), or you die and end up with a random small Monzilla and wait for the others to grow (because they are not being shot at) and so once they grow up you die with your current player, and then control shifts to the bigger Monzilla and then you can break the taller buildings. I kept this as a small game tactic, but I understand it is not very clear to figure out, and can be a bit annoying...so sorry for that.
Thank you for your reviews and opinions :)