Unfortunately I am going to have to recommend against buying this game at this time.
Mostly because the game feels very unfinished and is need of quite a bit of work.

That being said, the actual gameplay was rather fun and it has potential. Sadly that's about all the positive I can say about the game. I would recommend coming back to check on this game to see if the developers make changes to improve it. And will change my review if those changes are made.

Starting off there were a bunch of issues such as the mouse cursor being invisible, impossible to navigate to Exit the game with the gamepad, Unity config window lists dual display orientation backwards, menu navigation is extremely sensitive making it difficult to navigate the menu.
It bugged out on me intermission between Floor 4 and Floor 5. It's a guessing game to figure out where the highlighted item is or navigate any menu at all.
The fuel cost is upside down.
It was rather difficult to die. On floor 5 I ran out of ammo completely and was unable to locate or figure out how to get more ammo. Moving around the map dodging enemies trying to figure out what to do. Time ran out and screen goes red, gamepad shakes, but am still alive. After dying the gamepad was still frozen in vibration mode and was unable to navigate to anything from the death screen. Had to force quit.

Again, the game has potential, but at this time I don't believe it should be released as a finished game. It's far from and needs a lot of work. I know the devs can do it. Definitely would like to see this game evolve.

It's not a bad game, especially for the low price but the UI graphics are a bit amateur and the English is really bad: "toturial" for tutorial for example. Also it's not a "FPS" but an overhead third person view of the player (a tank). A HP display as a bar or something would be more useful than showing Hp as numbers.

The game, while poorly written, felt like it has potential to be fun. Likely this game should have come out in Early Access first, but otherwise I didn't hate playing it briefly.

The chief idea is that you are driving around in a tank while taking out throngs of enemies. You go from room to room FTL style using a variety of weapons in a twin stick shooter style. It definitely needs some balancing and and likely more things should be explained, but there is room to work around and make this game special.

Keep and eye on it.