izigame.me

I used to play this game a lot on the mobile version, and I was pleasantly surprised to see it on Steam aswell.
If you're into strategy games, Auralux might work for you.
The playstyle is rather slow and repetitive, which may result in a loop of growing your army, taking on empty planets, defend if you opposing factions attack, and repeat until you find a window to attack, hoping to not lose your planets in the process.
However, you do need to work out diverse strategies to overcome the opposing factions as the levels get harder (For example having to leave behind your starting planet in favour of a new start on a more favourable position), because you're generally put in a disadvantaging spot in comparison to your opponents. (This can become really frustrating afterlosing several times in the same levels)
If you're looking for a relaxing experience, Auralux can be a good pick, as long as you play the easier levels, but after that, be prepared for a grind.

Fun game for about 2.1 hours, then it's strictly luck as far as what the AI chooses to do. Most times you get ganged up on and can't do a thing. It goes from puzzle/RTS to pick on the player real quick. Some maps are even set-up in an unfair way as far as starting planets and the AI STILL chooses to come after you.

I love the very simplistic core concept of the game, but the unfair level design ruins it for me.
Most levels puts you in severe disadvantage, either it be your starting position, poorly positioned planets, more than 1 AI or all of the above. Fighting more than 1 AI doesn't feel like a fair fight. Sure, they do attack each other, but I got a feeling that they rather prefer attacking the player.
Too much of the playtime is just an endless tug of war, back and forth, between you and the other AIs.
Also, beware that the game is no longer maintained by the devs. Last update was back in September 2016.