This is going to be a difficult topic.
I’m going to discuss difficulty.
How games get it right and how they get it wrong.
There are two real types of difficulty out there: natural difficulty and artificial difficulty. Natural difficulty arises from the nature of the game itself. Artificial difficulty involves arbitrarily limiting the player in some way.
Super Mario Bros. is a classic example of natural difficulty. By the end of the first level, you have seen most of the abilities available in the entire game. The rest of the game challenges you with level design rather than by removing options. The game never stops you and forces you to be small or lose your Fire Flower. Also, every level can be entirely beaten with no power ups.
Even still, the stages get noticeably more difficult the further you go along. The first few levels are relatively benign. There are few pits and small number of enemies. Later the pits get larger and more frequent and on screen dangers become more numerous. This culminates in the penultimate level where to get the flag you must navigate a perilous series of jumps.
To use a modern example, Yakuza 4 often uses artificial difficulty to ramp up challenges. By the time you hit level 20 with a character, he is a one man wrecking crew. The various moves and finishes you have available makes most random encounters laughably pathetic. So in order to make certain fights more challenging they make most of your abilities useless or detrimental to the fight.
This winds up being a blemish on an otherwise excellent game. And also highlights the difficulty of difficulty.
A player must feel as if they are progressing if they are going to get engaged in your game. A lot of games through this through level based missions. The progression is literal. You can track your progress by the levels you have passed. In more open games progress can be harder to track. Since the majority of the map is open to you from the very start of the game, Yakuza indicates your progress by your characters abilities.
So when the game renders your abilities useless, it’s almost as if they’ve decided to move you backwards in the game. It’s a betrayal of expectations that destroys a player’s immersion.

