Great strategy game. It's got more original aspects to it than most games it there in this genre.. The developers have done a great job at letting us play through many historical moments with their weekly events, from the medieval ages and now upto the space age. Also that reminds me, everytime you upgrade your main building you go into the next age, so that's another cool aspect of the game! It keeps it fresh and less repetitive everytime. 
Like I said it's a great game but there are some big issues still occurring these days, like the odd hacker you see that makes a base undefeatable or a weird glitch every now and then.. But it's never a huge problem. 

In my honest opinion and for someone that's been playing for two straight years, I really do say it's worth the download. 

Also now their just (this week) getting into the Spaceage I suggest NOW is probably the best time to get into it due to events, freebies, cheaper buildings etc. 

If I had to rate it I'd go about an honest 8.5/10

Hope this helps.. if it did please like this post so I know. Thank you!

(Picture is my current base)