This game is a hidden jewel. People that go to the store page, may think: "Woah, mobile game on steam, so sad", but the truth is, I didn't have much fun with a game since months ago.
The game starts with a simple map, your base on one side, and enemies that come from the top. A quick tutorial reveals that you have to put different types of turrets, upgrade them, sell them if necessary, and defend your base. Seems easy, doesn't it?
You only have 2 turrets in the early levels, but as you proceed, you unlock more turrets. At the end of each game, you're assigned Victory Points depending on how good your performance was, and Perks, depending if you fulfilled the requeriments for one. With the victory points, you improve the level of upgrades of each turret, and when one is fully upgraded, you have the ability for 40 victory points to specialize that turret, making it more utile depending on what you choose. Regarding the perks, well, you have 3 types of perks, and as you unlock them, you put the ones that fit you the best.
The difficulty of the game is HARD. The first levels are kind of easy, but after some time, you will most likely get stressed at how screwed you are, that's when the Rewind option comes in hand. Basically, you have a rewind that you can use at the round you want, to start again that round, and delete everything you did, and the enemy did, that exact round. If you use it, you have to wait 3 more rounds until you can use it again.
This game is a fun little game, great for killing time, and for improving your strategies. I do recommend this game!
P.S: I got it for free thanks to Indie Gala, you only have to put your email, and you receive the code of the game for free, but I suggest buying it to support the developers!