Four types of games

Here's a grid I found in the teamliquid blog, which shows that games can be broken down into four categories:


The image is self explanatory, however no mobile games have been taken into consideration, hence below I've listed down 8 successful Android games, demonstrating what category they fit in:

Game	Category	Description
Paper toss	A	In this game, players are asked to flick a piece of paper into a trash can. Depending on the trajectory of the wind, a different angle will be required to complete the task. We’ve all once or twice tried to flick a piece rubbish into the bin like a professional basketball player and due to that familiarity the game is very easy to learn. In terms of mastery, the game is easy in the levels where the bin is positioned close to the player, however the ones that have bins positioned further away, require high precision, making it difficult to master.
Flow	B	Flow is almost patronisingly simple, with players just drawing lines between coloured dots to link them up. The only tricky part is not being able to draw one line across another. This puzzle requires a bit of thinking, but even the hardest level will take an average player 10 minutes at most to figure out, hence I put it in the easy to master category.
Angry Birds	B	‘Use the unique powers of each bird to destroy the pigs defences. Angry Birds features challenging physics-based gameplay and hours of replay value. Each level requires logic, skill, and force to solve.’ Given the fact that the game asks players to just drag and release a bird, launching it in the air, game play is very easy to pick up and understand quickly. Completing each level doesn’t require a high skill, due to the fact that players aren't asked to do an awful lot apart from releasing birds at the right angle, and performing their special abilities at the right time. Having said that Angry Birds isn't difficult to master, but what makes it popular is the high quantity of levels it offers.
Flappy Bird	A	Tap the screen to flap bird’s wings. Avoid the incoming obstacles. That one single mechanic is understood by millions of players from any demographics or age in seconds. As of any endless runner, Flappy Bird is technically impossible to master, given the fact that making a mistake is inevitable unless the player’s a robot. What makes it stand out of other games of this genre, is its very high difficulty from the very beginning. Interestingly, the creator didn’t follow tuning, which would make the game progressively harder, instead it is hard from the very beginning. Players get frustrated but not in a way that they want to stop playing, but the opposite - to carry on and on and on, until they feel like they've mastered the game. This, and the Mario related artwork, made it one of the most successful apps.
Retry	A	Quoting the original description: ‘You’re in the cockpit of a smoking, loop-the-looping, out of control, 8-bit jalopy of an airplane.  Fly through treacherous obstacles, and earn stars to unlock new worlds‘ The games controls are straightforward hence it's easy to learn - hold to accelarate, release to decelerate. Keep holding to perform a back loop. Similarly to Flappy Bird, Retry uses a tricky to handle twitch mechanic, making it difficult to master.
Fruit Ninja	A	Slice fruit, don’t slice bombs the description says. And indeed that’s all there is in terms of learning. When it comes to actually playing the game, as easy as it seems at the beginning it gets progressively more difficult as more bombs are being thrown in the air, making it tricky to avoid slicing them.
Super Digestion Moose	B	The only endless runner that I found manageable to master, without making the process too difficult. The aim is to tap the incoming fruits to feed the moose and avoid tapping mushrooms which poison it.  The game is quite tricky at the beginning, given the fact the hit boxes for the touchable objects are annoyingly small, but since game play doesn’t speed up or get more difficult overtime, eventually mastery is achievable.
Tippy Tap	A	In Tippy Tap the player is asked to touch the black tiles before they run off the screen. Tapping the wrong colour, or not tapping the right tile before it moves off the screen results to game over. Similarly to Fruit Ninja, Tippy Tap is easy at the beginning, but as the game starts speeding up, it is very difficult to keep up with the pace.

As the table demonstrates, not a single top downloaded mobile game is either hard to learn and easy to master (which is always terrible), or hard to learn and hard to master. The reason behind it, is because mobile gamers, as they're on the bus, at work, or chilling in bed, are the sort of audience who look for an easy non committing challenge. If they want to play something more complex, they'll turn their pc / console on. Having said that, it was a good decision from me to make easy to learn and hard to master games for mobile devices, because those are the ones that attract my audience the most, and sell the best.

Sources:
Game Study #1: Bushnell's Law [ONLINE] Available at: http://www.teamliquid.net/blogs/155657-game-study-1-bushnells-law [Accessed 9th November 2014]