dle games are a new and exciting type of game that I think will grow a lot in the next few years on mobile. Idle games, also known as Clicker games or "games that play themselves," are a strange type of game. For some reason, these games are the most popular on many of the most popular flash sites and are quickly climbing the charts on mobile. Make it Rain by 337 Games, Tap Titans by Game Hive, and now AdVenture Capitalist by Kongregate have all shown that this type of game belongs on the AppStore.

But why does this genre have so many fans? Why is this type of music even around? Why even talk about games that no one plays?

Idle games have become more popular on mobile because they are a great fit for the free-to-play style of mobile games today. The way idle games work makes them great for mobile sessions and keeps people playing for a long time.

What is an Idle Game?

Idle games, which can also be called "Clicker" or "Incremental" games, are all about managing income streams. The main thing that makes them different from simulation games is that they focus on how to make money.

The best example of an idle game is Cookie Clicker. When you tap the cookie, you get one cookie each time. You can buy upgrades with cookies. Upgrades either make it easier to tap the cookie (you now get two cookies for every click!) or make it so that more cookies are made automatically. These cookies are made automatically whether you tap or not. They are made even when you aren't playing.

This sounds too easy to be fun on paper. But give it a try yourself. Buying an upgrade is always a great feeling in and of itself. The growth curve is so fast that it quickly becomes very addicting. The most important part of the game is how fast resources are made. But there are problems with a single currency economy that grows so quickly. Costs to upgrade in the game go up very quickly. The game starts out with nice low numbers, but costs quickly soar into the trillions after just a few rounds. Most designers would be horrified to see a growth curve like this. Who wants to worry about numbers that are in the trillions? In AdVenture Capitalist, your costs will rise to more than 1 trillion billion dollars. Still, players like it. It's always nice to make progress. Players who have played long enough to get to these ludicrous numbers feel like they have done something great.

So, three of the top ten most played games on Kongregate are idle games. On Twitch, there are even channels where you can watch a computer play a game. This genre has grown a lot for no obvious reason.

No matter what you think about whether or not this is a "real" game genre, the way Idle games work is perfect for mobile. Mobile game designers can learn a lot from idle games about how to make games with good session design. Why are idle games so popular?

• It's always nice to get back.
• Sessions help the player leave on their own.
• The mechanics make it easy for the player to switch from micro to macro play.