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.