Rymdkapsel is a minimalist isometric strategy game set in space. It's akin to a survival game in that your goal is to build up your base to survive waves of enemies with increasing difficulty. Just like games like Clash of clans, you build different buildings that accomplish different tasks, and you "train" more units to defend your base. Unlike Clash of Clans and similar games, though, Rymdkapsel isn't interested in keeping you playing all day. The game isn't going for detail and the developers instead opted for simple, beautiful, minimalist graphics. The game is singleplayer only, and you'll be done with one session in a few hours, because after around wave 40, the enemies become nearly impossible to beat. While this may all sound bad, these features all actually contribute to the meditative feel of the game. While in other strategy games, you may rage as your base is destroyed, this game maintains a calm atmosphere. For every minute of those three hours of play, your mind will be absorbed in the game, calmly thinking about your next move. This game is short but worth every minute, and for that, you should definitely try this game. This game is $1.99 on Google Play, $3.99 on the App Store, and $3.99 on Steam.
Project Zomboid is an isometric zombie survival game which takes place in a completely open world. In it, you must gather and craft materials like most survival games, but in this one, there is an underlining, linear story. Unfortunately, I have only played the tech demo, which only gave me a small taste of the game, but even then, this game shows serious promise. The sad soundtrack, open world replayability, and simple isometric graphics make it an interesting play. In this game, you encounter huge hordes of zombies (fighting them is futile!) as well as other survivors. Some are friendly, some not so much. On the top right of your screen, the game will alert you of your character's specific status, from being well fed to having a panic attack. This game will keep you on your toes just trying to survive. You can download the free tech demo here, and you can get the full game off of Steam here.
Unturned is a free-to-play steam game that was featured by Alpha Beta Gamer a while back. Unturned is a zombie survival game in a semi-blocky style in that the world looks normal, while entities, items, and vehicles are made out of blocks. This game features multiplayer with a server hosting style similar to Minecraft. This game is a serious challenge, but also a ton of fun to play. The map is predetermined, but everything else is randomly generated. The game has driveable vehicles and also is populated with animals that can be killed and looted, along with, obviously, zombies that will try to kill you. This game is open world and has no real goal, meaning you can do whatever you want. This is possibly the best free survival game on steam, and you can get it here.