This is a first person shooter game, in which there are zombies infinitely spawning.
You can only take 5 hits from the zombie, then you are dead. Do not linger around too much because by the end many zombies will collect up, and you will have a lot of trouble.
Kill zombies, to set a high score and a to beat your own high score.
PS: The difficulty of the game can be set in the options menu. If not selected, the default difficulty will be medium. Also, this is an updated(bug-free, hopefully) version of this game, with a sensitivity slider which can be adjusted according to your wish.
You can get the offline version or downloadable version on: https://abhinav-arora.itch.io/zombie-siege