Viriax

Viriax is the latest game released by Locomalito, the creator of Hydorah. It is a vertical shooter set inside of a human body where you play a virus attempting to infect the patient. In the game you must jump and swim upwards towards the end of the level, dodging enemies and collecting power-ups. The biggest difference from normal vertical shooters is that moving drains your health, so you must constantly replenish it.

Their are six stages all representing parts of the body you are infecting and after completing any one of them you unlock the special ability that comes with that stage. Each of these stages are quite unique and have special enemies and environmental effects; For example the stomach has a continually rising ocean of acid that you must keep ahead of and the intestines are dark and you can only see a short distance. Additionally, these stages are procedurally generated, making them different every time you attempt them.

It is also worth noting, unlike Hydorah, this game is playable and even beatable (more of less) by people who are not particularly experienced in the shooter genre.

So for anyone who is interested they can check out Viriax here.

As far as I was able to get in a day.