I had fun with this game a few years back. It has a nice story, good for inbetween and a good challenge. While answering a message there, i've noticed that the game is now for free (since 2022). You might give it a shot.
https://store.steampowered.com/app/200390/Oil_Rush/ (https://store.steampowered.com/app/200390/Oil_Rush/)
Good Stuff!! Great Game
Thanks for the tip Anguille. I'm going to have to try this game out. I like the fact that the player does not build any units but rather relies on capturing buildings that autoproduce units at a set time interval. Reminds me of the autoproduce feature in Civilization III: Conquests.