game design (action adventure):
Action adventure games have been around as long as personal computers starting with text adventures. But in the 1990s with the SNES and Megadrive Players would be given structurally different levels to play and yummy graphics. In their most simple form we have Battletoads and Sonic, and upward more complex games like Lost Vikings. But one game on the pc had some real depth to it. Doom!

In this article I will make some stuff up and you wont laugh. No stop

action adventure game design holds 2 elements.
archetecture and objects
objects provide the chemistry of situations given to the player
the arcitecturual elements are the chemistry of gameflow, and provide additional chemsitry for situations.
combining situations and gameflow, you have a game.

situations determine what the player has to think about.
chemistry is what happens when you put 2 or more game elements together?
in a big open space, place 1 monster with the player. what happens?
add some arcitectural elements. did anything change? can it be done so anything changes?
what if you place 3 different enemies together? What if you change their relative {x,y,z} positions?
chemistry makes a game interesting, and gives you something new to think about.

the rules you place on the player for movement and interraction with other objects and arcitecture defines the range of chemistry which will be playable.
the player is the most important part of your game. give them power. give them limits.
pressing the spacebar to kill all enemies in the entire level instantly wont be interesting. Not without some kind of skill involved.
example, yes you can kill all the monsters. But the exit will vanish.
the gameplay becomes resisting the spacebar. This ability is also fit for a storyline, gameflow, or as a bonus.
gameflow example, there are tonnes of a robot spiders beyond a door and they will easily kill you.
but you collect 3 gems which fit into a magic circle, which activates a virus and shuts them all down.
caution on such game content. Other than learning not to use the door, there is no gameplay to offer.

As a game designer, expanding the chemistry of a game is central to adventure games.
Using situations and gameflow you create the impression of a location.
Where in reality, the same configuration of game elements can be repeated ad infinitum, destroying spacetime.
yes, destroying spacetime is the technically correct terminology (ok i'm lying).
But it takes interesting content to make an area unique. When you run out of unique situations, there is no more gameplay to make.

When players play a game, they focus on difficulty. Difficulty is a way to extend the time players spend on your game.
By providing a range of gameplay situations, each level of difficulty has more content to master.
This means not only players enjoy your game casually for longer, the entire game takes longer to play.
Gametime = difficulty * content

What gets you hooked on a game? What gives your game good diversity? Do graphics even matter? These are entirely seperate mysteries. But you can't play a

game if there's nothing to play! And who likes to spend hours on flappy bird? (Maybe this genre isn't for you)

Enjoy the rest of your day!