Up to 5 players. Clear 3 or more lines at once to raise a rival's floor.
Signing in is optional. With an account you get a profile and avatar, and you earn XP in online and CPU matches.
Online matches pay full XP. CPU matches pay 50% on Hard, 25% on Normal and 10% on Easy. A match counts as soon as it starts, so leaving or restarting mid-match scores as last place. Wins in under 20 seconds earn nothing. XP never drops below 0.