Mercury Meltdown Revolution navigates the fine line between variety and challenge perfectly, nothing is repeated too readily and anything new is quickly and seamlessly assimilated into the gameplay. Even when you complete a level there's an immediate sense that you want to go back and do it better; to collect all the bonuses, make it to the end with all your mercury blob intact and all within the time limit.
To aid in this there's a ghost system, so you can follow and compete against your last attempt and see where you can save time. As you become more adept you can see where shortcuts can be made, and though risky they'll always be worth it. It's just a shame Nintendo hasn't got its act together with online features sooner since online ghosts, scoreboards and other niceties would have added a great competitive element to the game.
Beyond the main single-player campaign, however, there isn't a great deal to look at. You can unlock a selection of 'Party Games', though these are rather piecemeal in nature and are barely worth looking it. Thankfully, there's enough in the main campaign to make up for the lack of alternative game modes. That it has this and near perfect Wii Remote utilisation makes it a sign of better things, and hopefully others will follow suit.
Mercury Meltdown Revolution does all the things many early Wii titles, particularly from third parties, haven't done. It uses the Wii Remote in an intelligent way that's easy to understand, and perform. Add this to some inventive and well thought out design, and it's a recipe for a great Wii puzzler that should entertain you while you wait for something meatier. Wherefore art thou Mario, Samus: anyone?