My audience will be in the range of 12 years and onwards, The reason being is because the game will have darkness, Scary Rats jumpy scene and guns.
It is important to understand my audience and what I can have in my game. So no blood, killing scenes or Rats eating human corps.My game will be a click and point like finding something in draws or under the table. the game will include Clues for the game not to be too hard for the younger audience.
Game conventions are great for young and old people to play together and if you ever go to one, you can have a better understanding how you can make your game for your target audience.
If you were making a game for 12 yrs+ you would fill your game with rich colors and fun sound effects or even rewards when completing a task.
If you were to make a game for adults you can but almost anything into a game. Blood, violence, bad language or killing other people.