Upon completing all six storylines, the player gains access to a seventh and final story which ties all the stories back together in a climactic boss battle and to ultimately resolve the plot.
Rather than start with a base skill set that you kept for the entire game, as you progressed in Sonic Adventure you would find upgrade items located in Adventure Fields and Action Stages that would bestow new abilities upon your character, such as Sonic's "Light Speed Attack", a move with a lengthy charge-up period that could be used to clear out entire groups of enemies at once.
As Sonic progresses though the game, "Action Stages" could be accessed from various entryways in Adventure Fields.
Gameplay: Gamma's feature mechanics that bare passing resemblance to shooters like Panzer Dragoon and Rez, where you move a laser crosshair around the screen in order to lock on targets and then release the fire button to take them all out in sequence.
Compared to other characters, Gamma has a unique health system in that a timer is constantly counting down to his inevitable death.
Eggman, who is feeding the monster Chaos Emeralds in order to increase its strength with the eventual goal of using it to conquer the world.
Knowing they can't let that happen, Sonic and Tails team up to find the Chaos Emeralds before Dr. Gameplay: The most traditional of the characters, Sonic's gameplay largely revolves around running to the end of the stage as quickly as possible while grabbing rings and destroying robots.
Sonic's own base set of skills had to be changed from previous title in order to more easily navigate in three dimensions, most notably with the addition of the "homing attack" -- which allowed Sonic to automatically strike a nearby enemy or object by performing a mid-air dash.
Homing attacks can even be chained together so long as more enemies are nearby.Gameplay: One of the slowest characters in the game, Amy Rose's gameplay can best be described as "stealth-lite".Every single one of her levels involves either running or hiding from the invincible ZERO robot.Story in Sonic Adventure is a much heavier focus than any Sonic title before it, with each character having their own unique plot thread that would often intersect with the other six storylines.Sonic and company were given cinematic cutscenes and fully-voiced dialog to help flesh the story out even further.After 1994's Sonic & Knuckles, Sonic the Hedgehog sort of fell off the map.