The combat system in Batman: Arkham Asylum is a simple yet it can be complex and frustrating to master depending on the player and what they want to accomplish. The combat system revolves around a continuous flow of combat elements that are that known to Batman, this combat system is commonly known as the FreeFlow Combat System. There are 9 elements that make up Batman's combat abilities in the game. These are Strikes, Counter, Cape Stun, Dodge, Ground Pound, Throw, Instant Takedown, Batarang, and Batclaw (note the exclusions of the Explosive Gel and Line Launcher). Each of these 9 elements count towards something called a "VARIATION", and bonuses are given for using as many of the 9 elements in a complete round.

The combat system indicator is located at the top left corner of the screen which shows Batman's Health, the Combo Meter directly below is indicated by a Hit Counter, followed by the Action Recap and the Score bars, and the occasional CRITIAL STRIKE indicator.

A combo begins when Batman performs a series of his combo elements against his enemies. The most commonly used elements are Strikes and Counters. The combo meter is signified by a hit counter, that will continue to run and be incremented until Batman reaches one of the Fail Out conditions:

Probably the most common Fail Out, and the most common for the button mashers with the FreeFlow Combat system. This occurs when Batman attempts a move that completely fails ending the combo streak.
Timed-Out Fail:
If for any reason if you fail to perform another action following a previous action for more than 1 second, the combo meter will fade ending your combo streak.
Taking a Hit:
If Batman takes a hit during his combo streak, it will end the combo.