Clicker Heroes is an idle game with an rpg skin on it. To begin with you click on the enemy with your mouse to deal 1 damage to an enemy per click. The game is broken up into levels. Each fifth level is a boss. On regular levels you have to defeat ten enemies to unlock the next level. Levels can be returned to once you have passed them, and you can stay on a level as long as you like. There is no time limit on normal levels. On boss levels you must defeat the boss in 30 seconds. If you fail the boss will respawn at full health.
Each time you defeat an enemy you gain gold. The gold can be spent to pay for heroes to join you. The first hero you can hire increases the effectiveness of your clicks, so that you can get beyond one damage per click. Gold can also be spent to level up the heroes so they are more effective.
The remaining heroes you can hire do a certain amount of damage per second to the enemy on the screen. They do this damage whether you are clicking or not.
There are also heroes that can unlock special powers that you can use. These powers have a cooldown time before they can be used again.
You also gain gold while the game is stopped. In fact this idle game you gain money whether the game is open in a tab or not, and you gain gold faster if it it closed than open.