I want to make an update in the near future which focuses on ironing out bugs and making the game mechanics more appealing. Were you confused about the current main goal of the game (reaching the portal) or due to the lack of instructions on movement/actions at the beginning?
The health indicator (vision radius) is changing very subtle at the beginning, but more obvious when the player's health has dropped below 50%. Information like this will be included and explained in the next update through an instruction screen on startup.