Free-Floor Fighting

A Fighting Game trope, where the fight isn't always limited to the plane that it starts on. This can open a lot more variation for stage effects, transitions, and action that ends in a completely different place from where it starts. This makes the matches more dynamic than the static counterpart, Fixed-Floor Fighting.

Because of the somewhat more random nature of the fights, battle tactics can be changed. Some combos may be cut short due to the environment not allowing them, a Ring Out or environmental damage may be more possible, etc. In this genre, a Launcher Move may simply knock an opponent through a predictable path, or open a new path through the game's environment.

Contrast Fixed-Floor Fighting. Outside of the Fighting Game genre, see Chase Fight.

Examples of Free-Floor Fighting include:

X-Men Next Dimension has levels where you can knock an opponent from one section down to another, dealing additional damage to them. For some levels, there are even multiple paths to make them fall.
Dead or Alive
Dragonball Z Budokai: In addition to knocking opponents to new areas, characters can also fly and introduce an entire new dimension to fights.
Battle Area Toshinden 2
Mortal Kombat vs. DC Universe has this. In most stages, you can go into "Vertical Kombat" by knocking an opponent off a ledge or through the floor, and some of them also allows you to smash them through walls and buildings into new areas. In both cases, you are able to keep hitting your opponent during the sequence, using a button-mashing minigame. In this series, this goes at least as far back as Mortal Kombat 3, which had stages in which uppercutting the opponent would send them to another stage directly linked to the previous one. In Deception and Armageddon, many stages had more than one area working in the same principle of the aforementioned Vertical Kombat system, except without the Kombat.
MadWorld has fights that are as simple as a plane (or rather, the ceiling of a familiar ship), or as complex as the entire castle of the last level you just played (i.e. The Courtyard, where you fight the Shamans).
Tatsunoko vs. Capcom: Uncharted Region of China has a breakaway floor, and Galactor's base has a path that can be adjusted. Both of these are affected by attacks that damage the ground.
Super Smash Bros.: Stages in this game vary from as constant as Final Destination to as chaotic as Big Blue (pictured above). In this stage you actually fight on top of cars as they race around a track. If you fall off of one and onto the asphalt, you get whisked off the side of the stage as the camera leaves you behind, resulting in a near-instant KO unless you can very quickly jump off and return to the stage.
Power Stone
Battle Stadium DON
Tekken 6 had certain stages where the floor would collapse. Tekken Tag Tournament 2 allows you to smash your opponent through some walls.
Street Fighter X Tekken has a twist on this in that you switch planes/areas in between rounds.