Archer Maclean's Mercury is a video game for the PlayStation Portable, first released in April 2005 in North America. In Japan, the game was released under the name [Hg] Hydrium. Mercury is a puzzle game developed by the eponymous British game programmer, Archer MacLean. In Mercury, the player tilts a level in order to get a drop of mercury to its appointed destination, in a similar fashion to Marble Madness. Differences include newer obstacles and the ability for the mercury to morph, split and transform around the levels. The game was originally designed to use a tilt sensor that plugged into the PSP's USB port, but this was never released.