The 9 main categories that flash games fall into are: Action, Arcade, Defense, Puzzle, Adventure, Simulation, Sports, Educational, and Multiplayer.

Action

An action game has moving objects and focuses on your timing, reflexes, hand-eye coordination, and quick thinking to achieve a good score. Most games have some action in them but aren't necessarily considered "action games." Most platformers are considered a type of Action games. Super Mario Bros. and Half-Life are good examples of action games.

Arcade

Arcade games are generally an off shoot with action games. What defines an Arcade game is usually a static background and very repetitive game play with ever increasing difficulty. Galaga and Pacman are good examples of these games.

Defense/Strategy

These types of games focuses on your resourcefulness and deal-making ability as you try to build and/or run something. In some games, your goal is to successfully build and run a city; in others, what you have to build or run can be anything from an army to a roller coaster. Some games have you in an immovable position with increasing amounts of advancing enemies, that you must stop. Advanced Wars, and all Tower Defense games are examples of this genre.

Puzzle

A puzzle game, also called a logic game, challenges your mind more than your reflexes. Many puzzle games are timed or limit the amount of time in which you can make a move. Games like Tetris and Sobokan are good examples of puzzle games.

Adventure/RPG

Adventure games let you control a character in an environment while the story is discovered. Unlike what happens in an RPG, your actions do not affect your character's overall abilities. An RPG is a game in which you, the game player, control a character in its environment. In this environment you encounter other beings and interact with them. Final Fantasy and The Legend of Zelda series are examples of these.

Simulation

Simulation games strive to simulate something in it's entirety. These games vary widely depending on what is being simulated. A Simulation of Piloting an aircraft can have a strong action theme, and a business Simulation will have a strong strategy theme. The Sims and the Tycoon series are Simulation examples.

Sports

A sports game is an action game with rules that mimic those of a specific sport. This could also be a type of simulation game depending on the view point. For instance, NHL 2002, by Electronic Arts, is an ice hockey sports game that plays like an action game. Whereas the Madden NFL games have more of a simulation feel.

Educational

In an educational game, the goal is to educate the player. This game can also be a part of another genre; for instance, you can have an educational puzzle game. An example of an Educational game would be one that teaches the player to type quicker through challenges.

Multiplayer

Multiplayer games pit more than one person against one another in a test of skills. This genre includes most previous ones, it simply test the skills of the players compared to one another. The most popular Multiplayer games are those of logic such as Chess, and Checkers.