I'm going to use Tiny Tower as an example to conveniently bring up the factoid of it being the first mobile free to play game i played. TT has you construct floors in an apartment building. You gain points by building different business that are essentially a floor in your tower. You also have to make residence floors so you have customers to shop in your sky scraper. The more floors you build the longer you have to wait, in real time no less. This is where the in game currency comes in. You can get rid of the wait time of the floors being constructed.
Instead of closing the game and doing something productive you can get rid of the wait time so you can continue being active in the game while you finish your business call. Business call is code for pooping. I made the term up a few years ago while i was a shift leader at Blockbuster video. "You guys hold the fort i gotta make a business call." See it sounds much more classy than admitting you're going to go into the dank staff washroom to play tiny towers while you dump.
In FF you build an army base and over time you can upgrade your base, defenses and battle units. Your base operates in the same manner as a Real Time Strategy game. You mine for oil and metal to build the tanks and planes you need to attack other players bases. The unique twist is the fact that you pick where your base is set up by putting in your address. The game then uses the street layout in the area of your neighborhood as the layout for your base. This gives the game a nice personalized feel.
Of course the game is just a mobile experience so you can't expect an entirely indepth RTS experience. The game is simplified and streamlined. Instead of having full unit control you pick a drop off point for your tanks around the enemy base. Then your forces roll into the enemy base on auto pilot and wreak havok all the while you can drop bombs via airstrike with pin point accuracy. When you defeat an enemies base you take some of their dog tags but if you loose they take yours. There are leader boards for the world all the way down to your city. Another unique feature is when you are attacked by another player you can get revenge on them and you awarded bonus dog tags for your effort but then they can do the same to you. The more you attack each other the bigger the bonus.
Problem is you never really get anything good without paying real money. Blood Brothers even limits the highest level of monsters to such rediculously high levels of in game currency you're basically left with no other option than to pay high amounts of money for a chance to draw for a powerful monster... Which means even if you do part with your hard earned money you can still get stuck with a shitty mage who has no real influence on your battles and you will end up getting ripped apart in all the PVP fights.
Eventually the frustration will be too much and you'll get sick of these games... all of them. Thanks but no thanks Blood brothers, Hell Fire, what ever that marvel game was called, that shitty transformers game and even Puzzle and Dragons. Yes Puzzle and Dragons is the top of the heap for these games but it's just a shitty stink heap anyway.