Asking how many levels to include in a game is sort of like asking how many paragraphs to include in your essay, or footsteps to take in your journey. Once you have a clear idea of your destination and your path, the question answers itself.
But it is a question worth considering because it leads to some interesting observations about game design.
What is a level?
Let's take a step back and look at what a level is, what it does, and what is its purpose.
- It introduces something new to the game, such as:
- Higher difficulty e.g. space invaders, pacman
- A new mechanic or puzzle e.g. donkey kong
- Progressing the story
- It's used to control pacing, giving a temporary lull in the action. Sometimes entire levels are devoted to this purpose, e.g. bonus stages
- It rewards the player, giving them a sense of progress e.g. the castle fireworks in Super Mario Bros
- It is often used as a checkpoint, somewhere players can resume if they fail in the game
- Historically, there were technical limitations to how much content you can have all together, so the game was split up into levels
Usually levels are used for many of the above reasons, but you may have noticed a common thread: levels encompass a unit of content, a self-packaged experience meant to be consumed as a whole. That isn't to say you must consume one unit of content at a time, but usually you (are encouraged or compelled to) finish playing after the end of a unit.
Units of content occur in many places, outside video games too, and there are many ways artists/authors encourage audiences to consume these in units. Books have chapters, and readers often - if they have a choice - stop and start reading between chapters. TV series have episodes, where each episode covers a self-contained story, sometimes within a greater story arc. Some media have only one unit of content, for instance movies are best enjoyed in a single sitting.
So it is with games; some have lots of small units of content, e.g. Angry Birds. Some have a single large unit of content, e.g. Civilization, where you are never encouraged to take a break until you've finally conquered the world, some 20-30 hours later. (Some days I think Sid Meier isn't aware that his players need to sleep.)
I believe the question "how many levels should I make" is better answered if you split it into two:
- How long should my "units of content" be?
- How long should my game be?
And divide the second by the first to get your answer.
How long should my levels be?
There are many factors that will affect the length of your levels:
How long do I want my players to play the game, at a time?
This goes right to the heart of your game design. If I'm standing in a line, I'd play Angry Birds or Candy Crush; if I were at home on a lazy weekend, I have more time and attention available - I could watch a movie.
How much time is necessary to teach the player a new mechanic?
This depends on the complexity of your game. A particularly complex strategy game might require long levels.
How much content do I need to meaningfully progress the plot?
For story-driven games, the appeal comes from seeing the plot unfold, and if your levels are too short there is simply not enough time to meaningfully move forward with your plot.
How long should my game be?
The answer to this one depends on quite a few things I've touched earlier. Your game should be:
- Long enough to tell the story, but your levels should be meaningful in terms of plot
- Long enough to teach the player about the game, but your levels should avoid being too repetitive
- Long enough to keep players interested, but keep in mind if it's worth the budget!
Sometimes there is no upper limit to the length of your game; you can keep making it longer so long as the cash is flowing in and the players are there. Just as they keep making episodes of The Simpsons by adding characters or even rehashing plots, you can add levels, new mechanics, rehash old mechanics... and sometimes the players love it!