The main idea explains the game in a general way. For example, “my game is about rescuing animals from a zoo”. You can start with the main idea then choose the mechanics, or the other way around.
When you’re about to play a new game, what questions come to your mind? Probably, “What kind of game is it?”, “What must I do?” and “What will then happen?”. The answers to these questions are related to the objectives and rules that conduct the actions of the players, which are the mechanics of the game.
The objective should be concrete and well defined in order to make players willing to participate. Examples: solving a problem, testing knowledge, finding something out, finishing first, accumulating points, being the fastest, eliminating enemies, beating the clock, etc. To help you come up with ideas for your game, think about your favorite games and their objectives.
Based on the objective, think about the rules: what a player or players can and cannot do in your game. To check if the game is coherent, make a mental map to describe the actions of the player(s) and its consequences.
Think about the place where your game will be played, and the elements needed, considering the target audience. A game for children will demand scenario and elements that are different from the ones of a game for teenagers, for example.
Outdoor games may need lines to limit the playing areas. Board games require a board with proper areas for the pieces and/or markers. Define these measurements and the design in order to make the development step easier.
Digital games require a scenario, but also a platform to run the game engine (set of features to build games) and some programming. There are websites that allow you to create your own game without any knowledge of programming, such as Draw your game app and sites like Sploder and GameMaker. If you want to test something more complex, you can go to Unity. Ask your parents or Informatics teacher to help you find the best option.
How many players will be needed? Will you have to design characters or pieces to play? Make these decisions by taking the target, the mechanics and the type of the game into consideration.
Besides the main idea, the mechanics and the characters, is there a story behind them that could improve your game? It’s possible that some ideas have come up during the process. Now that you form a core for your game, you have the chance to evaluate which ideas suit your design and which ones can be discarded.
It is time to write a set of instructions so that people can learn how to play. It must include the aim of the game, how it is played, what is or is not allowed, how the player becomes a winner, etc. If you are not sure how to start, look at the instructions for similar games.
The instructions for outdoor games are usually explained verbally, but you can write them down to be read out loud. Board games, may need an explanation about the storyline. You may also need to write an explanation about the board itself, such as where to place the markers, how to move them, etc.
Now you can make a list with all of those items from steps 1 and 2 and check if you have the answers to all of them.