Official story and features:
"The Mario Party series returns with more of everything. In the single-player Story mode, Brighton and Twila (otherwise known as the sun and the moon) are embroiled in a bitter feud over who's more impressive. It's up to Mario and his party-hearty cohorts to settle the spat and restore order to the cosmos. Multiplayer Party mode features more than 75 all-new mini-games and six game boards."
Story from Nintendo site
"- Clash with your friends in party-rockin' mini-games like Mowtown, Catch You Letter, Astaroad Rage and Cashapult.
- A new day and night system gives game boards and mini-games a split personality! Boards transform, characters emerge from hiding and mini-games change dramatically depending on the time of day.
- The game comes with a Nintendo GameCube Mic. Now you can control some furiously fun mini-game action with the sound of your voice.
- Faster movement: Speed around the board! Now there's less down time between turns and mini-games!"
Features from Nintendo site