The game is fun and free! It is challenging an you can play it for a long time. The events make it a lot more interesting as well!
However, since the last update progression is a bit difficult. Both the missions and in specific the raids dont give what is promised. I played 5 raids and only got money instead of evolve materials, which is pretty depressing since without these materials you are stuck. Also, I completed 4 missions today with quite a high succes probability (60, 80, 80, 90%) and all failed. This makes progression slower and makes playing the game less nice. I used to enjoy it much more but since the last update I feel like im stuck
But still its a great game! It also looks really nice!