Smarties: Meltdown is a third person game, apparently aimed at young children. The game is set on a giant Nestlé Smartie shaped factory ship which orbits the Earth. Dr. Soursweet is the main villain in the game, who aims to take over the Smarties factory. The main hero, the character played by the player, is Big Blue, who must battle to save the factory and the Smarties.
To do this, Big Blue has to explore the different areas of the factory, saving individual Smarties and destroying "Stroopers" - Dr. Soursweet's evil sugary creations. Big Blue must also find permanent upgrades, which improve various aspects of Big Blue and his "exosuit" (the suit in which he uses to run, shoot and jump). Some of the upgrades include "Choco Ray", which fires a blast of chocolate (with enough blasts, you can destroy Stroopers), and "Half Chocolate Jacket", which offers temporary protection against enemy fire.
Big Blue's exosuit runs on energy, which needs to be replaced after it is used up. Energy can be used by speeding up your run or by using the upgrades. Destroying Stroopers provides Big Blue with "energy balls". Big Blue has health and up to five lives - medikits and energy cells can also be found and collected.
The game is quite open-ended, with most levels containing large areas with plenty of Smarties to find. Most areas need you to collect a certain number of Smarties before you can access them, providing a challenge for younger players. There are a few different gameplay styles but these repeat themselves throughout the game. The entire game mostly has a 'platform' gameplay style, but there are some more action/adventure touches to certain parts of the game.
Source: Wikipedia, "Smarties: Meltdown", available under the CC-BY-SA License.