In this new mode you don't have lives - instead, you have characters. You'll start out playing as Sonic, but quickly you'll pick up either Mighty or Ray. At this point you can tag between the two at any time with a button press - and then as you explore you'll be able to add the other characters to your roster. You can only have two out at any given time, but item boxes and death will mean you're constantly swapping between the different members of the cast.