The story of Mercury Meltdown begins with your goal to guide a blob of mercury or multiple blobs through various mazes by tilting the game world. Hazards, such as being zapped, attracted, repulsed, eaten, or blown up, try to stop you. The game features a new visual style and many new stages.
The gameplay involves guiding the mercury blobs through mazes while avoiding hazards. The main change in the game is the ability to transform the mercury into three different states: Fast, Slow, and Solid. This allows for more puzzle-solving opportunities and a greater range of challenges.
Mercury Meltdown features 10 themed "Labs" with over 168 stages on the PSP version, offering a high replay value. The game also includes party games like Paint , Race , Rodeo , Shove , and Metrix* that can be unlocked by collecting bonus stars in the main game.
The attributes are measured based on performance, with rewards for high scores, completing levels within time limits, and finding all bonus items. The party games offer multiplayer options for up to five players via Wi-Fi on the PSP.