[In each Games Demystified column, developer Jeremy Alessi unpacks the technique behind a game's signature gameplay -- complete with a demo. Previously, he's covered gravity as applied in Super Mario Galaxy, Einstein-Rosen bridges in Portal, and the tiny-big world of Rolando. This time he's be covering the light-rail grinding of Dissidia: Final Fantasy.]

Dissidia: Final Fantasy is a far cry from typical Final Fantasy games because it is action-based. Taking the battles into real-time is one thing, but including an extreme sports-like element such as rail grinding really distinguished this version of Final Fantasy from previous efforts -- or any other fighting game for that matter.

The result is a digitally delicious dessert that blends Final Fantasy, Street Fighter, and Tony Hawk's Pro Skater into one decadent diversion.

There are so many unique gameplay elements present in this title that it was actually a bit difficult to decide what gameplay concept to cover.

In the end the light rails and their physics based mechanics grabbed my attention and are what separated this title from other RPG/Fighting games.

The concept of grinding over low friction rails is an old one. In fact, people have used rail transport since the sixth century B.C. The Diolkos Wagonway transported boats across the Corinth isthmus in Greece.

This early track system operated for 1300 years, stretched for 3.7 miles, and allowed slaves to push trucks along grooves of limestone, which formed the basis of the railway.

The trucks of this particular railway carried boats across the Corinth isthmus. This last fact highlights the basic premise of a rail system -- to reduce friction and allow for either quick or massive transport.

Obviously, the rails in Dissidia Final Fantasy are used for speed. Whether you need to escape a grueling attack or you just need to race across the map to collect an EX Core item, the rails are there to allow fast, accurate transport.

The question, as always, of course, is how can we simulate this precise method of transport within the world of a video game?

The answer is something called a spline path. There are numerous ways to create a spline path. In this edition of Games Demystified we'll break out of the purely algorithmic nature of the series and look at this mechanic from both the art and programming perspectives.