Thanks for the feedback.
Yeah, the concept of balancing out the weather to keep the environment green is the gameplay idea (at first there were other phases like a tornado phase that would have caused constant damage unless you changed the weather, but I was out of time to make the sprites and effects for that, even though the code was already made).
The objective is not to let the health fall to 0, the energy counter is just to try to make balancing it out harder (for example, after two or three rain/sun phases in a row). Health will not fall until the ground is wet or dry and will increase the damage after the tree dies. This where my attempt for a visual cue on when your player's health will start to drop and when the damage will increase.
Maybe a small introduction at the start would have made it a bit easy to understand the game concept.