As I note in the hands-on video you'll see below, Tunnel Ground still needs work for it to be a solid recommendation.
The menus are raw, the pace is slow, the UI fiddly, and mission objectives a little unclear.
But the game has continually gone through improvements since I was first made aware of it, the story is strong and very much central to the game, and the core gameplay is solid. It's a game with serious potential, basically.
It's definitely worth a look at our hands-on with Tunnel Ground, let me know in the comments whether you're keen to see more mech games on mobiles.