X² (formerly known as X) is a steel roller coaster operating at Six Flags Magic Mountain in Valencia, California. It is the world's first 4th Dimension roller coaster and was the final roller coaster conceived and installed by ride manufacturer Arrow Dynamics. The ride is unique in that the trains' seats pitch 360 degrees forwards and in reverse independent of the main chassis. The coaster initially opened to the public on January 12, 2002; numerous malfunctions delayed it from debuting in 2001 as was originally anticipated. On December 2, 2007, the ride closed for its transformation into X2. It was completely repainted, received new third generation vehicles, and featured new special effects including a pair of flame throwers. The ride reopened on May 24, 2008, following the upgrades.