Pros and Cons of Procedural Level Generation

Over the past few months I’ve been working on a 2D platformer game called Platform Pixels as a side project. A large part of making a game like this is designing and creating levels. I started off doing this by hand, but quickly realized that it was taking more time than I wanted.

To speed up the development cycle, I wrote a Procedural Level Generator to make levels for me. It can randomly generate a level for the game in seconds, which is a huge improvement.

Saving time is great, but there are many reasons why using a level generator is a bad idea. The goal of this post is to share what I’ve learned about level generation to provide insight to anyone considering a similar approach.

PRO: It Saves Time

As I mentioned in the introduction, manually creating levels is a lot of work. This would be bearable if it were a one-time job, but it’s far from that. Game mechanics change frequently (especially during the early stages), and these changes usually force the developer to modify or recreate existing levels. This is a lot of work, and after a doing it a few times, you end up not wanting to change too much because it will mean creating new content. This is not what you want when building a new game.

Level generation eliminates this barrier because it only takes seconds to create new levels instead of hours. This yields shorter iteration cycles and encourages the developer to make changes more often, resulting in a better game overall.

PRO: Prevents Getting Bored of the Game

One of the biggest side effects of creating levels by hand is the amount of play testing required to make them good. This didn’t seem like such a bad thing at first, but I quickly saw the downsides. There are two major downsides that come from overplaying a level.

How do I know it’s fun if I’ve played it a hundred times?

Play Testing Makes Levels Boring. How do I know a level is fun if I’ve already played it a hundred times? The only solution is to wait a few days and play it again but that takes time, and I don’t have that.

Play Testing Makes Levels Easy. How do I know a level is the right difficulty if I’ve played it a hundred times? By that point it’s usually so easy that I can beat it with my eyes closed. This makes creating a balanced set of levels almost impossible.

Again, level generation saves the day because it eliminates play testing almost entirely. You still need to play the levels that you generate, but only one or two times, instead of hundreds.

CON: Hard to Generate Visually Unique Levels

Perhaps the worst part about computers is that they aren’t creative or original. This makes building a level generator that outputs visually appealing and unique levels extremely difficult. Players don’t want to play the same boring thing over and over. Ideally, every levels should have a unique feature or style, but this is something that is hard to achieve even when creating levels by hand.

One way to improve on this is to make the generator more configurable. If I could tell the generator things like “generate a level that looks like a cave, and the entire floor is lava” that would be great! Unfortunately, this is very hard to do and probably not worth it. It would so much time to make a generator configurable like that that you might as well go back to making levels by hand.

So, if you’re thinking of building a level generator. First understand that the levels it produces won’t be as appealing as if a creative person made them by hand.

CON: Hard to Change The Generation Algorithm

Something I didn’t realize until after launching the initial Android beta was how much impact changing the generation algorithm would have on the levels. Due to the random nature of the generator, any small change to the code ended up generating a completely different set of levels. Here’s why that’s bad.

If level 5 of Beta 3 was really interesting and awesome, there is a high chance that it would be replaced by something less interesting and awesome in Beta 4. Every new generation is a gamble.

I put this down as a con, but it’s really not a huge deal most of the time. Yes, it sucks to lose a good level, but chances are that if you run the generator a few more times you’ll end up with a level that’s just as good (or better). Also, as you work on the generator, the average quality of level will hopefully go up.

BONUS: A Hybrid Approach

I was talking with my coworker Brad about level generation, and he suggested using the generator as a starting point, instead of expecting it to produce production quality levels. These levels could then be edited manually afterwards to tweak things and add visual flair. This provides the best of both worlds with almost no downsides, so that’s the approach I’m going to take.

Currently, my plan is to use the level generator during the beta stage of Platform Pixels. This gives me the fast iteration cycles needed to improve the game quickly, and also helps me focus on the game mechanics instead of the content. Then, once the mechanics are solid, I’m going to build off the generated levels and add visual appeal and uniqueness.

Wrap Up

If there’s anything I want you to take away from this post, it’s that level generators save time, but they can’t be creative enough to replace a human. If you really want awesome levels, you need to put in some manual work. However, this doesn’t mean that you can’t use a bit of technology to do some heavy lifting and assist you along the way.

I hope you got something valuable out of this post. Be sure to follow this blog for more updates on Platform Pixels development if you enjoyed reading this.