There are many definitions to define what is a game. We all have our own definition and we also played different games during our childhood to adulthood.
A game is a voluntary experience with at least the following:
- Have a clear goal
- Be able to interact with the world
- It needs to have some obstacles
- And we have rules to follow
Goal - can be used to rally the players into a simple overall task of your game - like finishing a level to progress in the story or simply to help the protagonist to achieve their goal through you the player.
Interaction - can be defined by the following - pressing buttons; touching the screen - rolling dices or just interacting with other players.
Obstacles - it needed to make the game more interesting and usually linked to the goals in your game like - enemies; platforms or a timer.
Rules - are the sets of do and don't inside your game - limitations of where you can go in the world by adding walls; gravity or physics applied to the players and the time limit imposed on the player. The rules can also be more abstract in the storyline or lore inside dialogs as well. Also, those rules can be modified or influenced by items or experience from the player to their advantage and disadvantage.